This report describes the typical weather at the Chicago Midway International Airport (Chicago, Illinois, United States) weather station over the course of an average year. It is based on the historical records from 1974 to 2012. Earlier records are either unavailable or unreliable.
Chicago, Illinois has a humid continental climate with hot summers and no dry season. The area within 25 mi of this station is covered by built-up areas (36%), oceans and seas (24%), grasslands (23%), croplands (14%), and forests (3%).
Over the course of a year, the temperature typically varies from 17Â°F to 84Â°F and is rarely below -0Â°F or above 93Â°F.
The warm season lasts from May 27 to September 18 with an average daily high temperature above 73Â°F. The hottest day of the year is July 12, with an average high of 84Â°F and low of 68Â°F.
The cold season lasts from November 29 to March 3 with an average daily high temperature below 41Â°F. The coldest day of the year is January 17, with an average low of 17Â°F and high of 30Â°F.
The length of the day varies significantly over the course of the year. The shortest day is December 21 with 9:09 hours of daylight; the longest day is June 20 with 15:14 hours of daylight.
The earliest sunrise is at 5:15am on June 12 and the latest sunset is at 8:30pm on June 29. The latest sunrise is at 7:27am on November 3 and the earliest sunset is at 4:20pm on December 10.
Daylight savings time (DST) is observed in this location during 2012, starting in the spring on March 11 and ending in the fall on November 4.
The median cloud cover ranges from 65% (partly cloudy) to 96% (overcast). The sky is cloudiest on December 25 and clearest on September 11. The clearer part of the year begins around May 24. The cloudier part of the year begins around October 28.
On September 11, the clearest day of the year, the sky is clear, mostly clear, or partly cloudy 52% of the time, and overcast or mostly cloudy 48% of the time.
On December 25, the cloudiest day of the year, the sky is overcast, mostly cloudy, or partly cloudy 78% of the time, and clear or mostly clear 22% of the time.
The probability that precipitation will be observed at this location varies throughout the year. Precipitation is most likely around December 31, occurring in 56% of days. Precipitation is least likely around August 12, occurring in 33% of days.
Over the entire year, the most common forms of precipitation are light rain, light snow, and thunderstorms.
Light rain is the most severe precipitation observed during 32% of those days with precipitation. It is most likely around October 20, when it is observed during 21% of all days.
Light snow is the most severe precipitation observed during 23% of those days with precipitation. It is most likely around January 15, when it is observed during 33% of all days.
Thunderstorms are the most severe precipitation observed during 21% of those days with precipitation. They are most likely around June 27, when it is observed during 19% of all days.
During the warm season, which lasts from May 27 to September 18, there is a 36% average chance that precipitation will be observed at some point during a given day. When precipitation does occur it is most often in the form of thunderstorms (45% of days with precipitation have at worst thunderstorms), light rain (36%), and moderate rain (13%).
During the cold season, which lasts from November 29 to March 3, there is a 53% average chance that precipitation will be observed at some point during a given day. When precipitation does occur it is most often in the form of light snow (53% of days with precipitation have at worst light snow), light rain (17%), and moderate snow (13%).
The likelihood of snow falling is highest around January 16, occurring in 43% of days. The season in which it is relatively likely for snow to fall spans from November 12 to April 1.
Either snow rarely accumulates at this location or snow depth measurements are unavailable or unreliable.
The relative humidity typically ranges from 44% (comfortable) to 91% (very humid) over the course of the year, rarely dropping below 25% (dry) and reaching as high as 100% (very humid).
The air is driest around May 3, at which time the relative humidity drops below 53% (mildly humid) three days out of four; it is most humid around August 13, exceeding 84% (humid) three days out of four.
Dew point is often a better measure of how comfortable a person will find the weather than relative humidity because it more directly relates to whether perspiration will evaporate from the skin, thereby cooling the body. Lower dew points feel drier and higher dew points feel more humid.
Over the course of a year, the dew point typically varies from 10Â°F (dry) to 67Â°F (muggy) and is rarely below -9Â°F (dry) or above 74Â°F (very muggy).
There are two periods in the year that are most comfortable: The first is between May 8 and July 4 and the second is between August 25 and October 7. The air feels neither too dry nor too muggy during these periods.
Over the course of the year typical wind speeds vary from 1 mph to 18 mph (light air to fresh breeze), rarely exceeding 26 mph (strong breeze).
The highest average wind speed of 12 mph (gentle breeze) occurs around April 3, at which time the average daily maximum wind speed is 18 mph (fresh breeze).
The lowest average wind speed of 8 mph (gentle breeze) occurs around August 8, at which time the average daily maximum wind speed is 14 mph (moderate breeze).