The climate of St. Petersburg is warm-summer humid continental (Koppen Dfb), featuring short, warm summers, and long, cold (though not severe by Russian standards) winters. This region is characterized by frequent changes in air masses, largely due to cyclonic activity. Westerly and northwesterly winds prevail in summer, westerly and southwesterly in winter.
St. Petersburg weather stations have had data since 1722. The highest temperature recorded in St. Petersburg is +37.1 °C and the lowest is −41 °C.
General characteristics The climate of St. Petersburg is warm-summer humid continental (Koppen Dfb), featuring short, warm summers, and long, cold (though not severe by Russian standards) winters. This type of climate is explained by the geographical location and atmospheric circulation characteristic of the Leningrad region. This is due to the relatively small amount of solar heat entering the Earth's surface and atmosphere.
Due to the small amount of solar heat, moisture evaporates slowly. The total influx of solar radiation here is 1.5 times less than in the south of Ukraine, and half as much as in Central Asia. There are an average of 75 sunny days per year in St. Petersburg. Therefore, days with cloudy, cloudy weather and diffuse lighting prevail for most of the year. The length of the day in St. Petersburg varies from 5 hours 51 minutes on the winter solstice to 18 hours 50 minutes on the summer solstice. The so-called "white nights" are observed in the city, coming on 25–26 May, when the sun sinks below the horizon by no more than 9°, and evening twilight practically merges with morning. The white nights end on 16–17 July. In total, the duration of the white nights is more than 50 days. The annual amplitude of direct solar radiation on a horizontal surface under clear skies ranges from 25 MJ/m2 in December to 686 MJ/m2 in June. On average, cloud cover reduces the arrival of total solar radiation by 21% per year, and direct solar radiation by 60%. The average annual total radiation is 3156 MJ/m2. The number of hours of sunshine is 1,628 per year.
According to long-term observations, St. Petersburg is characterized by a "heat island" effect, in which the temperature in the city is higher than in the surrounding areas.
Atmospheric circulation From the west and southwest, from the Atlantic Ocean, where the Azores anticyclone and the Icelandic minimum pressure are located, moist sea air enters the region, which has a mitigating effect on the climate. The city is characterized by warm, rainy summers and relatively mild winters. From the north and northeast, from the polar region of high pressure, cold and dry Arctic air masses enter the region, forming over the ice of the Arctic Ocean. It affects the climate of the region and the area of high pressure in Central Asia. From these areas, from the east and southeast, continental air enters the region, bringing dry and clear weather.
The air masses coming from the Atlantic have the greatest impact on the climate of the region. On average, winds from the western, north-western and south-western directions account for almost 46% (in autumn – about 50%) of all winds, winds from the northern and eastern directions – 28%, and south and south-eastern – 26%. The result of the change and interaction of air masses from different directions is the typical long-term variability of the weather and its instability throughout the year.
The urban conditions that create a special microclimate have a noticeable effect on the climate of St. Petersburg (as well as any large city). Dust, smoke, soot and other impurities in the air reduce solar radiation during the daytime, and at night they delay terrestrial radiation, slowing down the cooling of the Earth's surface. In summer, stone buildings and road surfaces become very hot and accumulate heat, and at night they give it to the atmosphere; in winter, the air receives additional heat from heating buildings. In summer, daytime temperatures in the center of St. Petersburg are 2–3 degrees higher than in the suburbs, and the relative humidity is 15–20% lower; in winter, the temperature difference can reach 10–12 degrees, and humidity up to 40%. The warmest part of the city is Nevsky Prospekt. The wind in the city is weaker than in the surrounding area in open areas (on average by 1–2 m/s)
Air temperature The average annual air temperature in St. Petersburg, according to observations for 1991–2020, is +6.3 °C. The lowest average annual air temperature, +0.9 °C, was recorded in 1809 and the highest temperature is +8.2 °C in 2020. The coldest month in the city is February with an average temperature of −5.0 °C, in January −4.8 °C. The warmest month is July, with an average daily temperature of +19.1 °C. The relatively small range of average daily temperatures in February and July (24.1 °C) characterizes the moderation of the St. Petersburg climate. The highest temperature recorded in St. Petersburg for the entire observation period is +37.1 °C (7 August 2010), and the lowest temperature is −41 °C (in 1758 and 1767).
The first day with an average positive temperature is in early April, and the first day with an average temperature below zero is in mid—November. The average duration of the entire period with a positive average daily temperature is 230 days, and with temperatures above +5 °C – 165 days.
Maximum and minimum average monthly air temperature (1744–2023)MonthJanFebMarAprMayJunJulAugSepOctNovDecHighest, °C1,5(2020)1,7(1990)3,6(2007)8,3(1921)15,9(1897)21,4(2021)24,4(2010)20,6(2022)17,0(2024)9,3(1775)4,4(2013)3,0(2006)Lowest, °C−21,4(1814)−19,5(1871)−11,5(1942)−3,7(1790)2,1(1867)11,1(1810)14,1(1837)12,6(1856)7,0(1894)−0,5(1880)−10,0(1774)−18,4(1788)
Precipitation, relative humidity, and cloud cover
The average annual precipitation in St. Petersburg is about 662 mm. But the amount of precipitation is about 200–250 mm higher than the evaporation of moisture, which causes increased moisture. The air humidity in St. Petersburg is always high. The annual average is about 75%, in summer – 60–70%, and in winter – 80–96%. Most precipitation falls from April to October, with a maximum in August and a minimum in March. During the year, the average number of days with precipitation is about 200 (from 13 days in April to 22 days in December), the average number of hours with precipitation per year is 1300. The rainiest summer was 1928, when 451 mm of precipitation fell (with the norm being 256 mm). The rainiest was in the summer of 1928, when 451 mm of precipitation fell (with a norm of 256 mm). The driest summer was the summer of 1858, when 98 mm of precipitation fell in St. Petersburg. In the 20th century, the rainiest days in St. Petersburg were in August 1935 and 1947.In August 1935, 65 to 90 mm of precipitation fell in the city in one day. Many streets were covered with a layer of 30–35 cm of water, the total volume of rain fell was about 35 million m3. On 8 August 1947, 76 mm of precipitation fell in the city, which exceeded the daily precipitation rate by 25–30 times.
The first snow usually falls in early November and persists until mid-April. Stable snow cover lasts from 110 to 145 days, on average from the beginning of December to the end of March. By the end of February, the snow cover reaches a maximum height of about 30–32 cm. Significant cloud cover is also typical in conditions of high humidity. On average, there are only 30 cloudless days in St. Petersburg per year. The highest cloud cover is in winter (over 80%), the lowest in summer (about 50%). Fogs are observed, especially in autumn and early winter; the average number of fog days per year is about 32.
Amount of precipitation 1740–2025 (daily after 1882) mmMonthJanFebMarAprMayJunJulAugSepOctNovDecMinimum231225512524Average for 1991–2020463635374769838657635651Maximum102929099139199166197190150118112Maximum per day232426295645697634372828 Snow depth (1890–2016), cmMonthJanFebMarAprMayJunJulAugSepOctNovDecAverage253130100000031118Maximum6368735310000163856
Characteristics of the seasons of the year
Winter Winter usually begins in St. Petersburg in November; its beginning coincides with the first snow (in November), establishment of snow cover (in December), ( but there are years when snow cover is established only in mid-January) and ice formation in the upper reaches of the Neva River. In the first half of winter, the weather is usually unstable, with frequent thaws. The sun is low, the day is short, and the snow cover is light. The air brought in from the west by cyclones cools quickly, and the water vapor contained in it condenses, which causes high clouds and fogs. During December, there are on average only 2 clear days. The second half of winter is noticeably colder than the first. The air coming from the west is getting colder, but less humid. Therefore, cloud cover decreases, fogs become less frequent, less precipitation falls, and Arctic air intrudes more often, lowering the temperature.
The nature of winter in St. Petersburg largely depends on the anticyclones and cyclones in the Atlantic. In years when the area of high pressure in the Atlantic expands, the Atlantic air intake increases in St. Petersburg, which makes winters warmer. According to long-term observations, such winters are repeated approximately twice in 11 years. So, in the winter of 1924/25, when the average January temperature was −0.5 °C, for 14 days the average daily temperature stayed above 0 °C, and one day reached +5 °C. That winter, the weather was cloudy, foggy, with strong winds, frequent snowfalls and thaws. Some of the warmest winters in St. Petersburg in the history of meteorological observations were observed at the beginning of the 21st century. During the period of weather anomalies in late 2006 and early 2007, new absolute temperature records were set. So, on 6 December 2006, the air temperature rose to +10.9 °C, which became the absolute maximum temperature not only for December, but also for the entire winter period in the entire history of meteorological observations. In the same winter period, the absolute maximum of January in the entire history of observations was beaten: on 10 January 2007, the temperature in St. Petersburg reached +8.7 °C, and stable snow cover that winter was formed only on 20 January.
At the same time, the winters of 2009/2010 and 2010/2011 were colder than normal and turned out to be unusually snowy. For example, during the period of 21–26 December 2009, 69 mm of precipitation fell in the form of snow, which is more than 1.5 monthly norms. And by the beginning of March 2011, the snow cover reached 73 cm, breaking the record of 1966 (68 cm). In addition, the second decade of February 2011, with an average temperature of −19.5 °C for 10 days, became the coldest in the history of observations.
During the years of expansion of the low pressure area in the Atlantic Ocean in the northeast, the influx of Arctic air increases, and St. Petersburg usually experiences cold winters. According to the long-term average data, this happens about once every 10 years. During the siege of Leningrad in the winter of 1941/42, the average January temperature was −18.7 °C (10 °C lower than usual), and on some days the temperature dropped to −30... -35 °C, there were no thaws, and the snow cover reached 60 cm. There was a similar cold winter in 1965/66. The absolute minimum of −35.9 °C was recorded on 11 January 1883.
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