The city was 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 greatly reduced this occurrence since the turn of the 21st century. Occasionally, the Foehn winds cause the temperatures to rise unexpectedly: on 22 January 2012 the daily high reached while on 22 February 2012 it reached . 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. thumb|left|Total monthly precipitation in Milan from 1940 to 2023. Data from open-meteo.com Summers in Milan are hot and humidity levels are high with peak temperatures reaching above . 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 precipitation occurs though, it is more likely to be accompanied by thunderstorms and hail. Springs and autumns are generally pleasant, with temperatures ranging between ; 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 (calm to gentle breeze), rarely exceeding (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 windy cities in Europe.
The city was 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 greatly reduced this occurrence since the turn of the 21st century Occasionally the Foehn winds cause the temperatures to rise unexpectedly on 22 January 2012 the daily high reached while on 22 February 2012 it reached  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 thumb|left|Total monthly precipitation in Milan from 1940 to 2023 Data from open-meteocom Summers in Milan are hot and humidity levels are high with peak temperatures reaching above  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 precipitation occurs though it is more likely to be accompanied by thunderstorms and hail Springs and autumns are generally pleasant with temperatures ranging between ; 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 (calm to gentle breeze) rarely exceeding (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 windy cities in Europe