December weather forecast and climate
Chicago, IL

An aerial view of the city of Chicago in Illinois, on the shores of Lake Michigan, with a superb view of the sandy beach of Oak Street
An aerial view of the city of Chicago in Illinois, on the shores of Lake Michigan, with a superb view of the sandy beach of Oak Street
December is the start of the cold winter in Chicago with the first substantial snowfall. The average temperatures are in the freezing 21°F (-6.1°C) to 35°F (1.7°C) range; a few nights register below 10°F (-12.2°C), and one or two even drop below 0°F (-17.8°C).
Snowfall registers, on average, 8.5" (215.9mm) accompanied by 2.3" (58.4mm) of icy rain. The daily sunshine reduces to 4 hours with short days of 9 hours in December. Dense fog routinely spills due to the lake breezes, as cloudy skies become the norm of the day.
Layer up, as December is the windiest month of the year in Chicago.

What is the average temperature in December in Chicago?

In Chicago, in December, the average high-temperature is 35.2°F (1.8°C), and the average low-temperature is 22.6°F (-5.2°C).
Average temperature in December - Chicago, IL
  • Average high temperature in December: 35.3°F

The warmest month (with the highest average high temperature) is July (84.2°F).
The month with the lowest average high temperature is January (31.5°F).

  • Average low temperature in December: 22.7°F

The month with the highest average low temperature is July (67.5°F).
The coldest month (with the lowest average low temperature) is January (18.2°F).

Average humidity in December - Chicago, IL
  • Average humidity in December: 75.5%

The month with the highest relative humidity is December (75.5%).
The month with the lowest relative humidity is May (64.1%).

Average rainfall in December - Chicago, IL
  • Average rainfall in December: 2.6"

Wettest months (with the highest rainfall) are May and June (4.1").
The driest month (with the lowest rainfall) is February (1.9").

Average rainfall days in December - Chicago, IL
  • Average rainfall days in December: 11.1 days

The month with the highest number of rainy days is May (11.4 days).
The month with the lowest number of rainy days is September (8.2 days).

Average snowfall in December - Chicago, IL
  • Average snowfall in December: 8.7"

The month with the highest snowfall is January (11.5").
Months with the lowest snowfall are May, June, July, August and September (0").

Average snowfall days in December - Chicago, IL
  • Average snowfall days in December: 6.7 days

The month with the highest number of snowfall days is January (8.1 days).
Months with the lowest number of snowfall days are May, June, July, August and September (0 days).

Average sea temperature in December - Chicago, IL
  • Average sea temperature in December: 42.4°F

The best month for swimming (with the highest average sea temperature) is August (73.9°F).
The coldest month (with the lowest average sea temperature) is February (36.9°F).

Average daylight in December / Average sunshine in December - Chicago, IL
  • Average daylight in December: 9.2h

The month with the longest days is June (Average daylight: 15.2h).
The month with shortest days is December (Average daylight: 9.2h).

  • Average sunshine in December: 3.4h

The month with most sunshine is June (Average sunshine: 10.4h).
The month with least sunshine is December (Average sunshine: 3.4h).

Average UV index in December - Chicago, IL
  • Average UV index in December: 1

Months with the highest UV index are June and July (UV index 9).
Months with the lowest UV index are January and December (UV index 1).

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