Helsinki has a humid continental climate similar to that of Hokkaido or Nova Scotia coastal. Owing to the mitigating influence of the Baltic Sea and North Atlantic Current (see also Extratropical cyclone), temperatures during the winter are higher than the northern location might suggest, with the average in January and February around −4 °C (25 °F).
Winters in Helsinki are notably warmer than in the north of Finland, and the snow season is much shorter in the capital, due to it being in extreme Southern Finland and the urban heat island effect. Temperatures below −20 °C (−4 °F) occur a few times a year at most. However, because of the latitude, days last 5 hours and 48 minutes around the winter solstice with very low sun (at noon, the sun is a little bit over 6 degrees in the sky), and the cloudy weather at this time of year exacerbates darkness. Conversely, Helsinki enjoys long daylight during the summer; during the summer solstice, days last 18 hours and 57 minutes.
The average maximum temperature from June to August is around 19 to 22 °C (66 to 72 °F). Due to the marine effect, especially during hot summer days, daily temperatures are a little cooler and night temperatures higher than further inland. The highest temperature ever recorded in the city was 33.2 °C (91.8 °F), on 28 July 2019 at Kaisaniemi weather station, breaking the previous record of 33.1 °C (91.6 °F) that was observed in July 1945 at Ilmala weather station. The lowest temperature ever recorded in the city was −34.4 °C (−30 °F), on 10 January 1987 although an unofficial low of −35 °C (−31 °F) was recorded in December 1876. Helsinki Airport (in Vantaa, 17 kilometres (11 mi) north of the Helsinki city centre) recorded a temperature of 33.7 °C (92.7 °F), on 29 July 2010, and a low of −35.9 °C (−33 °F), on 9 January 1987. Precipitation is received from frontal passages and thunderstorms. Thunderstorms are most common in the summer.