Milan features a mid-latitude humid subtropical climate and accumulations of snow can occur: the historic average of Milan’s area is 25 centimetres (10 in) in the period between 1961 and 1990, with a record of 90 centimetres (35 in) in January 1985. In the suburbs the average can reach 36 centimetres (14 in) The city receives on average seven days of snow per year.
The city is often shrouded in thick cloud or fog during winter, although the removal of rice paddies from the southern neighbourhoods and the urban heat island effect have reduced this occurrence in recent decades. Occasionally, the Foehn winds cause the temperatures to rise unexpectedly: on 22 January 2012 the daily high reached 16 °C (61 °F) while on 22 February 2012 it reached 21 °C (70 °F). Air pollution levels rise significantly in wintertime when cold air clings to the soil, causing Milan to be one of Europe’s most polluted cities.
Summers in Milan are hot and humidity levels are high with peak temperatures reaching temperatures above 35 °C (95 °F). Due to the high humidity, urban heat effect and lack of wind, nighttimes often remain muggy during the summer months. Usually the summer enjoys clearer skies with an average of more than 13 hours of daylight: when precipitations occur though, there is a higher likelihood of them being thunderstorms and hailstorms. Springs and autumns are generally pleasant, with temperatures ranging between 10 and 20 °C (50 and 68 °F); these seasons are characterized by higher rainfall, especially in April and May. Relative humidity typically ranges between 45% (comfortable) and 95% (very humid) throughout the year, rarely dropping below 27% (dry) and reaching as high as 100% Wind is generally absent: over the course of the year typical wind speeds vary from 0 to 14 km/h (0 to 9 mph) (calm to gentle breeze), rarely exceeding 29 km/h (18 mph) (fresh breeze), except during summer thunderstorms when winds can blow strong. In the spring, gale-force windstorms may happen, generated either by Tramontane blowing from the Alps or by Bora-like winds from the north. Due to its geographic location surrounded by mountains on 3 sides, Milan is among the least windiest cities in Europe.