Climate - Chicago (Illinois)

Chicago is the largest city of Illinois, and it's located in the American Midwest, at nearly 42 degrees north latitude, along the banks of Lake Michigan. Here, the climate is continental, with cold winters (when there are many periods below freezing) and hot summers. Although the city is located at a middle latitude, in winter it is cold because the North American land mass cools down a lot, and polar air outbreaks are frequent. Given the distance from the sea and the exposure to different types of air masses, temperature changes are frequent.
Here are the average temperatures recorded at the Chicago Midway International Airport.

Precipitation amounts to 960 millimeters (37.9 inches) per year and is well distributed over the seasons, at least in frequency, while in terms of quantity, the winter is the driest season. In winter, and also in spring and autumn, weather fronts pass over the area, while in late spring and summer, when they become less frequent, thunderstorms can form in the afternoon or evening: it is no coincidence that the wettest period is from May to August.
In winter, precipitation mainly occurs in the form of snow. An average of 98 centimeters (38.5 inches) of snow falls per year; every once in a while, a snowfall can be seen already in October, while in spring, sometimes it can snow even in April. The record belongs to the winter of 1978-79, when a total of 228 cm (90 in) of snow fell. Here is the average precipitation.

Winter in Chicago runs from late November to early March and is very cold, to the point that the average temperature is reminiscent of Northern European cities. But at least, the days here are not as short as in the Nordic countries.
Snowfall is frequent, so much so that it snows for several days in a month; sometimes, real snowstorms can occur.
Polar cold spells are accompanied by the blizzard, the north wind blowing in gusts and able to heighten the feeling of cold. Particularly cold periods, with minimum temperatures dropping to -20 °C (-4 °F), occur practically every year, and sometimes they can even drop to around -30 °C (-22 °F). The coldest record is -32.8 °C (-27 °F) and was set in January 1985 at O'Hare airport.
Although the temperature remains below freezing (0 °C or 32 °F) even during the day for weeks, sometimes it can exceed freezing also in winter, resulting in melting snow and possible rainfall. Every so often, the phenomenon called "ice storm" (or freezing rain) can also occur, that is, rain falling on frozen ground, freezing everything, roads, trees, light poles, cars etc.

Spring, from mid-March to May, is an unstable season, characterized by different situations and temperature changes: initially cold in March, with snowfalls and frosts still quite frequent, it advances gradually, between the first warm days and the return of cold weather conditions. In early April, it can still snow; on the other hand, during the month the first warm days can occur, with highs around 30 °C (86 °F). In fine weather, a cool (or even cold) breeze in the afternoon blows from the lake, which is felt especially in the eastern districts of the city. In May, it can still be cold at night, especially at the beginning of the month, while on other occasions, it can be hot, with highs above 30 °C (86 °F). In April and May, in the first fine and warm days, the first thunderstorms in the afternoon or in the evening can occur.

Summer, from June to August, is hot, humid and sunny, with some afternoon or evening thunderstorms. There may be some pleasant days, with highs around 25/27 °C (77/81 °F) and cool nights, but also real heat waves, with highs around 35 °C (95 °F) and beyond. In the worst moments, the temperature can reach as high as 40 °C (104 °F), as happened in July 2012.

Autumn, from September to November, is the (relatively) quietest period of year. However, we can not rule out early cold weather periods or the return of warm temperatures, and even waves of bad weather. In early September, the weather is still often characterized by heat and humidity, with sunshine and some afternoon thunderstorms, while later, it becomes milder. In early October, particularly mild days, even warm, can occur, but in the course of the month there may be slight frosts. Between late October and early November, usually after the first night frosts, a mild period, with highs above 20 °C (68 °F), can occur: it's the so-called Indian summer. However, during the month of November it can get cold, with the first snowfalls and intense frosts.



The amount of sunshine in Chicago is very good in summer, when there are several sunny days, and it's good in May and September. In the other months, the sun shines a little less often, however, some sunny days can also occur in the middle of winter. There are on average 2,500 hours of sunshine per year.

Near Chicago, Lake Michigan is very cold in winter (and it can partially freeze on colder winters, and fully on the coast), while in summer it is still cool, but becomes almost acceptable for swimming, at least in August, or for those who do not suffer from the cold. However, it depends on the period: after a series of a few hot days in a row, the lake can become more temperate.
Here are the average lake temperatures.

Best Time

The best period to visit Chicago is the beginning of autumn, from early September to mid-October. You can also choose the spring, from mid-April to late May, but it is a more unstable and windy season. However, in both periods, you may run into a bit of cold at night, or hot temperatures during the day, or some rainy days.
Those who can stand the heat can also choose the summer, which has longer days and more hours of sunshine, but also the risk of very hot days. However, the summer can also give acceptable periods (and maybe, cool nights as well).

Chicago - Weather by month

Based on the period 1991-2020

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In January, the coldest month of the year, the weather in Chicago is usually very cold. The average temperature is of -3.0 °C (27 °F), with a minimum of -6.7 °C (19.9 °F) and a maximum of 0.7 °C (33.2 °F).
On the coldest nights of the month, the temperature usually drops to around -19 °C (-2.5 °F). However, it dropped to -30 °C (-22 °F) in January 2019.
On the warmest days of the month, the temperature usually reaches around 12 °C (53.5 °F). However, it reached 18.3 °C (64.9 °F) in January 2008.
Precipitation amounts to 50 mm (2 in), distributed over 11 days.
The day lasts on average 9 hours and 30 minutes.
There are on average 4.5 hours of sunshine per day. So, the sun shines 46% of the time.
The average humidity is 73%. Hence, the air is normally humid.
The average wind speed is 18 kph (11 mph).

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In February, the weather in Chicago is usually very cold. The average temperature is of -1.0 °C (30 °F), with a minimum of -4.8 °C (23.3 °F) and a maximum of 2.9 °C (37.1 °F).
On the coldest nights of the month, the temperature usually drops to around -16 °C (3.5 °F). However, it dropped to -27.3 °C (-17.1 °F) in February 1996.
On the warmest days of the month, the temperature usually reaches around 14 °C (57.5 °F). However, it reached 22.8 °C (73 °F) in February 2000.
Precipitation amounts to 50 mm (2 in), distributed over 9 days.
The day lasts on average 10 hours and 35 minutes.
There are on average 5 hours of sunshine per day. So, the sun shines 46% of the time.
The average humidity is 69%.
The average wind speed is 18 kph (11 mph).

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In March, the weather in Chicago is usually quite cold. The average temperature is of 4.6 °C (40 °F), with a minimum of 0.1 °C (32.2 °F) and a maximum of 9 °C (48.2 °F).
On the coldest nights, which normally occur at the beginning of the month, the temperature usually drops to around -10 °C (14 °F). However, it dropped to -20 °C (-4 °F) in March 2002.
On the warmest days, which normally occur at the end of the month, the temperature usually reaches around 22 °C (71.5 °F). However, it reached 30 °C (86 °F) in March 2012.
Precipitation amounts to 60 mm (2.4 in), distributed over 11 days.
The day lasts on average 12 hours and 0 minutes.
There are on average 6 hours of sunshine per day. So, the sun shines 50% of the time.
The average humidity is 65%.
The average wind speed is 18 kph (11 mph).

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In April, the weather in Chicago is usually mild. The average temperature is of 10.7 °C (51 °F), with a minimum of 5.5 °C (41.9 °F) and a maximum of 15.9 °C (60.6 °F).
On the coldest nights, which normally occur at the beginning of the month, the temperature usually drops to around -2 °C (28 °F). However, it dropped to -6.1 °C (21 °F) in April 2018.
On the warmest days, which normally occur at the end of the month, the temperature usually reaches around 27.5 °C (81.5 °F). However, it reached 32 °C (89.6 °F) in April 2002.
Precipitation amounts to 95 mm (3.7 in), distributed over 12 days.
The day lasts on average 13 hours and 25 minutes.
There are on average 7 hours of sunshine per day. So, the sun shines 53% of the time.
The average humidity is 60%.
The average wind speed is 18 kph (11 mph).

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In May, the weather in Chicago is usually very mild. The average temperature is of 16.9 °C (62 °F), with a minimum of 11.5 °C (52.7 °F) and a maximum of 22.3 °C (72.1 °F).
On the coldest nights, which normally occur at the beginning of the month, the temperature usually drops to around 4 °C (39.5 °F). However, it dropped to -0.6 °C (30.9 °F) in May 2020.
On the warmest days, which normally occur at the end of the month, the temperature usually reaches around 31.5 °C (89 °F). However, it reached 36.1 °C (97 °F) in May 2012.
Precipitation amounts to 115 mm (4.5 in), distributed over 12 days.
The day lasts on average 14 hours and 35 minutes. So the days are long.
There are on average 9 hours of sunshine per day. So, the sun shines 62% of the time.
The average humidity is 62%.
The average wind speed is 16 kph (10 mph).

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In June, the weather in Chicago is usually warm. The average temperature is of 22.2 °C (72 °F), with a minimum of 17.1 °C (62.8 °F) and a maximum of 27.3 °C (81.1 °F).
On the coldest nights, which normally occur at the beginning of the month, the temperature usually drops to around 9.5 °C (49.5 °F). However, it dropped to 3.9 °C (39 °F) in June 2003.
On the warmest days, which normally occur at the end of the month, the temperature usually reaches around 34 °C (93.5 °F). However, it reached 37.8 °C (100 °F) in June 2012.
Precipitation amounts to 105 mm (4.1 in), distributed over 11 days.
The day lasts on average 15 hours and 10 minutes. So the days are long. June 21, the summer solstice, is the longest day of the year in the Northern Hemisphere.
There are on average 10.5 hours of sunshine per day. So, the sun shines 68% of the time.
The average humidity is 63%.
The average wind speed is 14 kph (9 mph).

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In July, the warmest month of the year, the weather in Chicago is usually warm to hot. The average temperature is of 24.8 °C (77 °F), with a minimum of 20.1 °C (68.2 °F) and a maximum of 29.5 °C (85 °F).
On the coldest nights of the month, the temperature usually drops to around 14.5 °C (58.5 °F). However, it dropped to 12.8 °C (55 °F) in July 2013.
On the warmest days of the month, the temperature usually reaches around 35.5 °C (95.5 °F). However, it reached 41.1 °C (106 °F) in July 1995.
Precipitation amounts to 95 mm (3.7 in), distributed over 10 days.
The day lasts on average 14 hours and 50 minutes. So the days are long.
There are on average 10.5 hours of sunshine per day. So, the sun shines 69% of the time.
The average humidity is 63%.
The average wind speed is 14 kph (9 mph).

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In August, the weather in Chicago is usually warm to hot. The average temperature is of 23.8 °C (75 °F), with a minimum of 19.4 °C (66.9 °F) and a maximum of 28.2 °C (82.8 °F).
On the coldest nights of the month, the temperature usually drops to around 14.5 °C (57.5 °F). However, it dropped to 9 °C (48.2 °F) in August 2009.
On the warmest days of the month, the temperature usually reaches around 34 °C (93.5 °F). However, it reached 38.3 °C (100.9 °F) in August 1991.
Precipitation amounts to 110 mm (4.3 in), distributed over 9 days.
The day lasts on average 13 hours and 50 minutes.
There are on average 9 hours of sunshine per day. So, the sun shines 66% of the time.
The average humidity is 66%.
The average wind speed is 13 kph (8 mph).

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In September, the weather in Chicago is usually warm. The average temperature is of 20.0 °C (68 °F), with a minimum of 15.2 °C (59.4 °F) and a maximum of 24.7 °C (76.5 °F).
On the coldest nights, which normally occur at the end of the month, the temperature usually drops to around 7 °C (45 °F). However, it dropped to 1.6 °C (34.9 °F) in September 1995.
On the warmest days, which normally occur at the beginning of the month, the temperature usually reaches around 32.5 °C (90.5 °F). However, it reached 35.6 °C (96.1 °F) in September 2013.
Precipitation amounts to 80 mm (3.1 in), distributed over 8 days.
The day lasts on average 12 hours and 25 minutes.
There are on average 7.5 hours of sunshine per day. So, the sun shines 61% of the time.
The average humidity is 64%.
The average wind speed is 14 kph (9 mph).

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In October, the weather in Chicago is usually mild. The average temperature is of 13.2 °C (56 °F), with a minimum of 8.5 °C (47.2 °F) and a maximum of 17.8 °C (64.1 °F).
On the coldest nights, which normally occur at the end of the month, the temperature usually drops to around 0 °C (32 °F). However, it dropped to -3 °C (26.6 °F) in October 1996.
On the warmest days, which normally occur at the beginning of the month, the temperature usually reaches around 28 °C (82.5 °F). However, it reached 31.1 °C (88 °F) in October 2005.
Precipitation amounts to 85 mm (3.3 in), distributed over 10 days.
The day lasts on average 11 hours and 0 minutes.
There are on average 6 hours of sunshine per day. So, the sun shines 57% of the time.
The average humidity is 64%.
The average wind speed is 16 kph (10 mph).

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In November, the weather in Chicago is usually quite cold. The average temperature is of 5.9 °C (43 °F), with a minimum of 2 °C (35.6 °F) and a maximum of 9.8 °C (49.6 °F).
On the coldest nights, which normally occur at the end of the month, the temperature usually drops to around -7 °C (20 °F). However, it dropped to -12.8 °C (9 °F) in November 2019.
On the warmest days, which normally occur at the beginning of the month, the temperature usually reaches around 20 °C (68 °F). However, it reached 25 °C (77 °F) in November 2016.
Precipitation amounts to 60 mm (2.4 in), distributed over 10 days.
The day lasts on average 9 hours and 50 minutes.
There are on average 4 hours of sunshine per day. So, the sun shines 38% of the time.
The average humidity is 68%.
The average wind speed is 17 kph (11 mph).

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In December, the weather in Chicago is usually very cold. The average temperature is of 0.0 °C (32 °F), with a minimum of -3.4 °C (25.9 °F) and a maximum of 3.4 °C (38.2 °F).
On the coldest nights of the month, the temperature usually drops to around -14.5 °C (5.5 °F). However, it dropped to -22 °C (-7.6 °F) in December 2000.
On the warmest days of the month, the temperature usually reaches around 14 °C (57.5 °F). However, it reached 21.7 °C (71.1 °F) in December 2012.
Precipitation amounts to 55 mm (2.2 in), distributed over 11 days.
The day lasts on average 9 hours and 10 minutes. December 21, the winter solstice, is the shortest day of the year in the Northern Hemisphere.
There are on average 3.5 hours of sunshine per day. So, the sun shines 37% of the time.
The average humidity is 73%. Hence, the air is normally humid.
The average wind speed is 17 kph (10 mph).