Weather In London In Sep

London has a temperate oceanic climate (Köppen Cfb classification), featuring mild temperatures year-round, frequent cloud cover, and precipitation distributed fairly evenly throughout the year with no pronounced dry season.[1] This maritime-influenced climate results in relatively few extremes compared to continental locations, though the city's urban heat island effect can amplify warmth, making central areas up to 10°C hotter than surrounding rural zones, particularly at night during calm, clear conditions.[2]Representative long-term averages from Heathrow (commonly used for London climate data) show an annual mean maximum temperature of 15.67°C and mean minimum of 7.83°C for 1991â2020, with July typically the warmest month (mean maximum 23.89°C) and January/February the coolest (around 8â9°C maxima).[3] Annual rainfall averages 614.98 mm, spread across about 112 days with â¥1 mm precipitation, while annual sunshine totals 1,674.81 hours.[3] The urban environment and proximity to the Atlantic Ocean moderate seasonal swings, contributing to London's reputation for changeable, often overcast weather.London occasionally experiences notable extremes, including a record high of 40.2°C recorded at Heathrow on 19 July 2022 during a major heatwave.[4] The city also hosts some of the world's longest continuous meteorological records, with observations dating back centuries at historic sites such as Kew Gardens and Greenwich.[5] These factors, combined with the urban heat island and ongoing climate trends, distinguish London's weather from that of many other major cities.

Overview Current conditions As of 8 February 2026, around 13:00 GMT, London experiences temperatures of 52â53 °F (11 °C), with a feels-like temperature of 50â51 °F due to wind and humidity effects. Conditions are mostly cloudy, winds blow from the south at 5â8 mph, and relative humidity stands at 78â81%. These values reflect conditions at the time of observation and remain subject to change; live updates are available from authoritative sources such as the Met Office [6] or BBC Weather [7].

This snapshot aligns with London's typical maritime-influenced weather, though transient variations occur frequently. Climate classification London has a temperate oceanic climate (Köppen-Geiger classification Cfb).

This classification indicates a temperate climate (C) with no dry season (f) and warm summers (b), where the coldest month averages above 0°C (but below 18°C), the warmest month averages below 22°C, at least four months average above 10°C, and all months receive adequate precipitation without a pronounced dry period.[8]The Cfb designation reflects London's position in Western Europe, where the climate is strongly moderated by its proximity to the Atlantic Ocean and the North Atlantic Current (part of the Gulf Stream system).

This maritime influence produces mild temperatures year-round, relatively narrow annual temperature ranges, and consistent moisture compared to continental climates at similar latitudes.[8]Such oceanic characteristics distinguish London from more extreme continental or Mediterranean climates, resulting in a regime of frequent cloud cover, humidity, and precipitation rather than marked seasonal contrasts.[9] General characteristics London's weather is characterized by a temperate oceanic climate (Köppen Cfb classification), resulting in year-round mild temperatures with limited seasonal extremes due to the moderating maritime influence of the Atlantic Ocean.[10]This maritime setting produces frequent cloud cover and a high frequency of rainy days, with precipitation distributed relatively evenly throughout the year rather than concentrated in distinct wet or dry seasons.[10]Such conditions foster a generally damp and overcast atmosphere, setting London apart from climates with sharper seasonal contrasts or prolonged dry periods.[11]The city also possesses some of the world's longest continuous meteorological records, with precipitation observations dating to January 1697 at Kew Gardens and temperature records beginning in 1841 at the Royal Observatory in Greenwich.[12][10] Temperature patterns Average temperatures London's temperatures remain mild throughout the year, characteristic of its temperate oceanic climate with strong maritime influence from the Atlantic.Heathrow Airport, located in western London at low elevation, serves as the standard reference station for the city's climate averages due to its long continuous record and representation of lowland urban-fringe conditions.

For the 1991â2020 period, mean daily maximum temperatures range from 8.4 °C in January to 23.9 °C in July, while mean daily minimum temperatures range from 2.7 °C in January and February to 14.2 °C in July. The annual mean temperature is 11.7 °C.[3]The monthly averages at Heathrow (1991â2020) are as follows:These values reflect the mild seasonal progression, with the warmest months in July and August and the coolest in January and February.[3]Temperatures vary modestly across London due to topography and the urban heat island effect.

Higher-elevation areas such as Hampstead experience slightly cooler conditions; for 1991â2020, Hampstead's annual mean temperature is approximately 11.0 °C, about 0.7 °C lower than at Heathrow, primarily due to its greater elevation.[13] The urban heat island effect further warms central and built-up areas, particularly at night, contributing to differences of several degrees compared to surrounding rural zones, though annual averages show smaller variations.[11] Record highs and lows London's record high temperature stands at 40.2°C (104.4°F), recorded on 19 July 2022 at Heathrow Airport during an exceptional heatwave that saw the United Kingdom exceed 40°C for the first time.[14][15][4] This value was provisionally measured at Heathrow early in the afternoon and later confirmed as a new benchmark for the capital.The record low temperature is â16.1°C (3.0°F), observed at Northolt on 1 January 1962 amid a severe cold wave that affected much of the United Kingdom.

This remains the lowest minimum temperature documented in the London area from long-term records at sites including Northolt, Heathrow, Kew Gardens, and Greenwich.Other notable extremes include exceptionally low daily maximum temperatures, such as â8.3°C, which has occurred on multiple historical dates, highlighting periods of persistent cold in the capital's meteorological history. These records underscore London's vulnerability to both unusually high and low temperature extremes despite its generally mild oceanic climate.

Precipitation Rainfall distribution London's rainfall is characterized by a relatively even distribution throughout the year, a pattern typical of its temperate oceanic climate influenced by maritime airflows from the Atlantic. This results in no pronounced dry season, with precipitation occurring reliably across all months.[3]The annual average precipitation in London is approximately 600â630 mm, depending on the specific site.

At Heathrow Airport, the 1991â2020 average is 615 mm, while records from Kew Gardens indicate around 628 mm over the same period.[3][16]Monthly rainfall amounts are broadly similar, typically ranging from about 39â45 mm in drier spring months such as March and April to higher values of 65â67 mm in autumn months such as October and November.

A modest peak occurs in autumn and winter, particularly from October to January, reflecting the influence of Atlantic weather systems.[3][16]The city experiences an average of 110â114 days per year with at least 1 mm of rainfall, based on long-term observations. At Heathrow, this averages 112 days annually (1991â2020), with monthly counts ranging from about 8 days in summer to 11â12 days in autumn and winter.

Kew Gardens records show a similar figure of around 114 days.[3][16] Snowfall and wintry precipitation Snowfall in London is infrequent compared to more continental climates, owing to the city's maritime influence and mild winters, but wintry precipitationâprimarily snow or sleetâoccurs mainly between November and April.

In lower-lying areas of southern England, including London, snow or sleet falls on an average of 12-15 days per year.[11]Days with lying snow (at least 50% snow cover at the observation time) are fewer, averaging around 5 per year in inland areas such as those around London.[11] The urban heat island effect in central London often raises temperatures by several degrees during cold spells, reducing both the frequency and duration of lying snow compared to surrounding rural or suburban areas.[17]Heavy accumulations are rare, but notable events have caused significant disruption.

In January 1987, persistent heavy snow showers brought over 35 cm of level snow in areas either side of the Thames Estuary, with 52 cm recorded at East Malling in Kent.[11] In March 2005, drifts up to 30 cm affected parts of the North Downs in Kent and East Sussex.[11] Such episodes, though occasional, can lead to travel chaos and winter disruptions in the capital.[11] Sunshine, cloud cover, and fog Annual sunshine hours London receives an average of approximately 1,600 to 1,700 hours of bright sunshine per year, according to long-term climate averages from the Met Office for Heathrow, a site representative of London conditions.[3] The 1991â2020 period records an annual total of 1,674.81 hours, higher than earlier baselines such as 1,519.44 hours for 1961â1990, reflecting variability over time.[3]Sunshine duration varies markedly by season due to London's maritime-influenced climate and persistent cloud cover.

Summer months deliver the peak, with July averaging 217.81 hours, June 208.39 hours, and May 207.49 hours. Winter months are far lower, typically under 80 hours, with December at 54.96 hours, January at 61.09 hours, and February at 78.81 hours. Transitional seasons show intermediate values, such as April at 176.67 hours and October at 115.17 hours.[3]This distribution underscores the impact of frequent overcast skies, which limit sunshine despite London's moderate daylight hours throughout the year.

The city's annual total remains modest compared to sunnier European locations, where clearer conditions allow totals often exceeding 2,000 hours.[3] Fog and smog episodes London has long been prone to fog episodes, particularly radiation fog formed under clear skies and calm conditions that allow ground-level cooling. Historically, these natural fogs were exacerbated by coal smoke from domestic fires, factories, and power stations, producing thick, yellow-green "pea-soupers" that reduced visibility to mere metres and became a defining feature of the city's atmosphere from the Industrial Revolution onward.

In the 19th century, London experienced an average of 80 dense fog days per year, with some areas recording up to 180 in peak years like 1885.[18]The most severe and infamous episode was the Great Smog of 1952, which blanketed the city from 5 to 9 December.

An anticyclone created a temperature inversion that trapped cold air near the ground, preventing dispersion of pollutants; this combined with widespread coal burning for heating during a cold spell and easterly winds carrying additional pollution to produce exceptionally dense smog up to 200 metres thick. Visibility dropped to near zero in many areas, halting transport, infiltrating buildings, and causing widespread respiratory distress.

The event resulted in an estimated 4,000 immediate deaths from respiratory and cardiovascular conditions, with some analyses suggesting a total toll as high as 12,000 when including longer-term effects.[19][20][21]Such lethal smog events prompted major legislative changes. The Great Smog directly led to the Clean Air Act 1956, which established smoke-control zones, banned black smoke emissions, and encouraged shifts to smokeless fuels, with further strengthening through the 1968 Act. These measures, alongside transitions to cleaner heating sources like gas and electricity, dramatically reduced smog episodes.

Severe pea-soupers, once recurrent in winter, became rare after the mid-20th century, and modern fog in London is typically natural radiation fog without the heavy pollution that once transformed it into toxic smog.[19][20][21] Wind and atmospheric conditions Prevailing winds London's prevailing winds are predominantly from the south-west, driven by the North Atlantic's westerly airflow that influences much of the United Kingdom.[22] These winds carry moist maritime air from the Atlantic Ocean, contributing to the city's mild, damp climate.[23]Annual mean wind directions typically fall between west and south, though with notable seasonal shifts.

South-westerly winds predominate during winter, summer, and autumn, while springâparticularly April and Mayâsees a marked increase in northerly or north-easterly winds, sometimes equaling or exceeding south-westerlies due to blocking anticyclones over the North Atlantic.[23] In detailed hourly data for central London, westerly directions dominate for most of the year (approximately 11 months), peaking at around 40% frequency, while a brief period in late spring favors northerly winds up to about 28% at their peak.[24]Average hourly wind speeds exhibit clear seasonal variation, with windier conditions from October to April (averaging over 11.5 mph) and calmer periods from May to September.

The windiest month is typically January (around 13.1 mph), while July is the calmest (around 9.8 mph). Overall annual averages hover between 9 and 11 mph, with lighter winds more common in summer.[24][25] Gusts are generally moderate under typical conditions, though they increase during frontal passages associated with the prevailing south-westerlies. Air quality and pollution London's air quality has improved significantly in recent decades, with reductions in key pollutants such as nitrogen dioxide (NOâ) and fine particulate matter (PMâ.â ) driven primarily by policies targeting road transport emissions.

Road traffic remains the dominant source of NOâ and NOx emissions, while PMâ.â arises from vehicle exhaust alongside contributions from domestic heating, industrial activities, and regional sources.[26][27]The Ultra Low Emission Zone (ULEZ), launched in central London in 2019 and expanded across the city in 2023, has been instrumental in these gains.

Within three months of the 2019 implementation, roadside NOâ concentrations fell by 19.6% in central London, with NOx dropping by 28.8%; spillover effects produced smaller but notable reductions in inner and outer areas.[27]Between 2016 and 2023, annual average roadside NOâ levels declined by 49%, the number of monitoring sites exceeding the UK annual legal limit fell from 56 to 5, and hours exceeding the hourly limit decreased by 99%.[26]PMâ.â levels also improved, with no active monitoring sites exceeding the interim World Health Organization target in 2023 for the first time on record.

Following the 2023 ULEZ expansion, air quality improved at 99% of monitoring sites across London, with estimated NOâ reductions of 27% overall since 2019 and 31% lower PMâ.â exhaust emissions from cars and vans in outer London.[26][28]Despite progress, NOâ and PMâ.â concentrations still exceed World Health Organization guidelines in some locations, indicating that further action on non-traffic sources is required to meet long-term air quality goals.[27] Seasonal weather Spring (MarchâMay) Spring in London, spanning March to May, marks a gradual transition from the cooler, wetter winter to warmer summer conditions, characterized by rising temperatures, increasing sunshine, and changeable weather with frequent showers.Average daily maximum temperatures increase steadily from around 11.7°C in March to 15.0°C in April and 18.4°C in May (1991â2020 Heathrow averages), while minimum temperatures rise from about 4.1°C to 9.1°C over the same period.

This warming trend reflects the lengthening days and higher sun angle, though nights can remain cool, and occasional late frosts occur in March.[3]Sunshine hours rise significantly through the season, from approximately 124 hours in March to 177 hours in April and over 207 hours in May, as cloud cover decreases and clearer skies become more common.

Rainfall is moderate and fairly consistent, averaging 39â46 mm per month, typically delivered as showers rather than prolonged rain, contributing to the season's variable and often changeable nature.[3]The weather can be unpredictable, with calm, dry spells alternating with showers and, less commonly, wintry flurries in early March.

Spring is also notable for the blooming of flowers, trees, and plants across parks and green spaces, signaling renewal as pollen levels rise and nature awakens after winter.[29] Summer (JuneâAugust) Summer (JuneâAugust) is the warmest season in London, featuring the highest average temperatures of the year alongside the longest daylight hours and a peak in convective activity such as thunderstorms.Average daily maximum temperatures during this period typically range from around 21â24 °C, based on long-term data from Heathrow (a representative site for London).

For the 1991â2020 period, monthly average maxima are 21.6 °C in June, 23.9 °C in July, and 23.4 °C in August.[3] These values reflect the moderating influence of London's maritime location, which prevents extreme heat in most years while allowing for comfortable warmth.Daylight reaches its annual maximum around the summer solstice (typically 20â21 June), providing up to approximately 16 hours and 38 minutes of daylight in London, with sunrise before 5:00 am and sunset after 9:00 pm.[30] This extended photoperiod contributes to the season's relatively high sunshine totals compared to other times of year.Thunderstorms occur most frequently in summer, driven by convective instability.

Southeast England, encompassing London, averages 15â20 thunderstorm days annually (1971â2000 data), with the majority concentrated in this season.[31] These events often bring short, heavy showers and occasional lightning, though widespread severe storms remain uncommon.Temperatures occasionally exceed 30 °C during brief warm spells, though such conditions are not typical of the average summer.[3] Autumn (SeptemberâNovember) Autumn in London brings a noticeable cooling trend, increased rainfall, and the onset of fog as the season progresses toward winter.Daily maximum temperatures cool progressively, averaging around 20°C in September, dropping to about 16°C in October, and reaching approximately 11°C in November (based on 1991â2020 Heathrow data, representative of London).[3] Mean minimum temperatures follow a similar decline, from roughly 12°C in September to 5°C in November.[3] This cooling is accompanied by shorter days and often unsettled weather, with Atlantic systems bringing changeable conditions.[32]Rainfall typically increases through the season, with monthly totals around 50 mm in September rising to over 65 mm in both October and November, reflecting a wetter pattern as autumn advances.[3]Fog and mist become more frequent from late autumn onward, particularly in November, as cooler air temperatures, longer nights, and calm conditions favor their formation, often resulting in reduced visibility during mornings.[33]The season is also marked by vivid foliage changes, with leaves turning yellow, red, and brown in a burst of color before falling, especially vibrant after dry summers followed by sunny days and cool nights.[32] Winter (DecemberâFebruary) Winter in London, from December to February, brings the city's coolest weather, with mild but damp conditions, frequent cloud cover, and occasional wintry showers.Average daily maximum temperatures range from about 8.5°C to 9.2°C, while minimum temperatures typically fall between 3.2°C and 3.8°C (1991-2020 averages at Greenwich Observatory)[34].

At Heathrow, a commonly referenced site for London-area data, maxima average 8.4°C to 9.0°C and minima 2.7°C to 3.1°C over the same period[3].Rainfall remains frequent, with monthly totals of 40â59 mm and rain occurring on 9â11 days per month on average, making winter one of the wetter seasons[34][3].Snowfall is occasional, occurring on roughly 16 days per year across the city, though significant accumulations are rare and mostly limited to trace amounts or light coverings (see Cold snaps and heavy snow for details on notable events).Daylight hours are at their shortest, averaging around 8 hours in December and increasing gradually through February, while sunshine remains limited, with monthly totals typically 44â78 hours and skies overcast or mostly cloudy 65â72% of the time[35].

Air frost occurs on about 6 days per month, adding to the chilly feel on clearer nights. Extreme weather events Heatwaves and high temperatures London has experienced several notable heatwaves in recent decades, with extreme high temperatures becoming more frequent and intense due to climate change.The highest temperature ever recorded in London was 40.2°C at Heathrow Airport on 19 July 2022, during an unprecedented national heatwave that saw the UK exceed 40°C for the first time.

This surpassed previous records by a significant margin and was accompanied by a record high minimum temperature in parts of the London area, such as 25.8°C at Kenley Airfield.[14][36]Earlier significant heat events include the 2003 heatwave, which set a UK record of 38.5°C in Kent and brought prolonged high temperatures to London, and the 2018 summer heatwave, which featured temperatures reaching the mid-30s Celsius across southern England, including London, amid an exceptionally warm season.[37][36]Climate change is increasing the frequency, duration, and intensity of such heatwaves in the UK, including in London.

Met Office analysis indicates that extreme heat events are becoming more common, with warm spells lengthening and the likelihood of temperatures exceeding 40°C rising under human-induced warming. For example, summers as warm as 2018 are now several times more probable than in the late 20th century, with projections showing further increases in hot extremes.[37] Cold snaps and heavy snow London occasionally experiences cold snaps accompanied by heavy snow, though such events are infrequent given the city's temperate oceanic climate influenced by the Atlantic.

These episodes can cause widespread disruption to transport networks, schools, and daily life in the densely populated capital.One of the most notable cold snaps occurred during the severe winter of 1981â82, particularly in December 1981, when a major cold wave brought exceptionally low temperatures and snow to much of the United Kingdom.

This period is remembered for its intense and prolonged freezing conditions, with significant snowfall affecting London and surrounding areas.[38]The winter of 1962â63, often called the "Big Freeze," stands out as one of the most prolonged and severe on record. Freezing temperatures and heavy snow persisted for months, bringing London to a near standstill.

Roads became impassable, rail services were disrupted, and in some cases, essential supplies such as milk were delivered by alternative means amid the deep snow cover.[39][40]In February 1991, an unusual cold spell delivered deep snowfall to central London, with up to 20 cm recorded at St James's Parkâthe greatest snow depth in the city since reliable records beganâleading to extensive transport chaos and closures.[41]More recent heavy snow events, such as those in December 2010, caused major disruptions including near-total shutdowns at Heathrow Airport and gridlock on roads across the capital.[40]These rare but impactful cold snaps and heavy snowfalls demonstrate the vulnerability of London's infrastructure to extreme winter weather, often resulting in travel paralysis, school closures, and challenges to emergency services.

The historical record low temperature for the London area stands at â17.4°C, recorded during the 1981 cold snap. Flooding and storms London has a long history of flooding from the River Thames, driven by combinations of high tides, storm surges, and heavy rainfall.

The last major tidal flood in central London occurred on 7 January 1928, when a storm produced record water levels, breaching embankments from Greenwich to Hammersmith, flooding areas including Whitehall and Westminster, killing 14 people, and leaving thousands homeless.[42] A devastating North Sea storm surge in 1953 killed 307 people along the east coast of England and sent high waters into London's East End, highlighting the urgent need for improved defences.[43][42]To address these risks, the Thames Barrier was constructed between 1974 and 1982 near Woolwich and officially opened in 1984.

This 520-metre movable barrier, with 10 gates that can hold back thousands of tonnes of water, protects 125 square kilometres of central London, including 1.42 million people and property worth £321 billion. Since becoming operational, it has closed 221 times for flood defence purposes, including a record 50 closures during the winter of 2013/14 amid an exceptionally high tide and storm season, preventing any properties in central London from flooding.

No comparable tidal flooding has occurred in central London since its completion.[43][42]Heavy rainfall and storms continue to pose challenges, often leading to surface water or fluvial flooding in areas beyond the barrier's primary protection. For example, intense storm events have caused widespread UK flooding in recent years, though the barrier has effectively mitigated tidal threats to central London.[43]Climate change exacerbates future flood risks through rising sea levelsâpotentially up to a metre by 2100âand more frequent intense storms, increasing the likelihood of storm surges and higher river flows.

The barrier, originally designed for protection until 2030, is now expected to remain effective until around 2070 due to robust maintenance, but upstream and downstream defences require raising earlier than planned, with some upgrades needed by 2050.

The Thames Estuary 2100 plan, managed by the Environment Agency, outlines phased adaptations, including defence height increases of 30â60 cm downstream by 2040 and decisions by 2040 on long-term optionsâsuch as barrier upgrades or a new structureâto maintain protection through the century, with a new system operational by 2070.[44][42][43] Urban and local climate variations Urban heat island effect The urban heat island (UHI) effect in London causes the built-up central areas of the city to experience higher temperatures than surrounding rural or suburban regions, primarily due to human modifications of the landscape.[2]The main causes include the high thermal capacity of urban materials such as concrete, asphalt, buildings, and pavements, which absorb solar radiation during the day and release stored heat at night; reduced vegetation cover, which limits evaporative cooling and shade; and anthropogenic heat from traffic, buildings, and energy use.[2][45]Temperature differences vary by time of day, weather conditions, and location, but the central London area can be up to 10°C warmer than rural surroundings during extreme events, such as the 2003 heatwave, with nighttime differences often reaching 5â6°C on calm, clear summer nights.[2] Typical urban-rural contrasts are around 4â5°C in central areas, while localised hot spotsâsuch as parts of Kilburn and South Hampsteadâcan exceed 7°C warmer than nearby green spaces like Regent's Park.[45] Daily maximum UHI intensity has reached 5.07°C in long-term observations at central sites.[46]This effect exacerbates heat extremes, amplifying daytime highs and significantly elevating nighttime minimum temperatures, which reduces opportunities for cooling and increases health risks during heatwaves, as well as energy demand for cooling.[2][45] Microclimates across London London exhibits a variety of microclimates due to its varied topography, the presence of the River Thames, and differences in land use and vegetation across the city.Elevated areas such as Hampstead in north London are typically cooler than lower-lying central districts.

Hampstead Heath, with its higher altitude and extensive green spaces, creates a noticeably cooler environment, particularly during summer, offering relief from higher temperatures elsewhere.[47]The River Thames influences nearby areas by moderating temperatures and providing cooling breezes, especially in summer. Locations close to the river, such as those near Kew Gardens, benefit from this effect, contributing to subtle differences in local conditions compared to inland sites.[47]Vegetation cover plays a significant role in local temperature variations, with greener areas remaining cooler than densely built-up zones.

For example, a low-vegetation area in Kilburn and South Hampstead was over 7°C hotter than Regent's Park, which has high vegetation cover, demonstrating the cooling impact of parks and gardens.[45]Weather observation stations across London reflect these microclimate differences. Stations like Kew Gardens, situated near the Thames and amid botanical gardens, often record slightly different temperatures compared to airport sites such as Northolt or Heathrow, which are influenced by open tarmac and lower vegetation.

During the July 2022 heatwave, Heathrow recorded a peak of 40.2°C, Kew Gardens approximately 40.1°C, and Northolt approximately 40.0°C, illustrating site-specific variations.[48][45]

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Weather in London?

This snapshot aligns with London's typical maritime-influenced weather, though transient variations occur frequently. Climate classification London has a temperate oceanic climate (Köppen-Geiger classification Cfb).