Normal High and Normal Low temperatures for the first day of each month, the 15th of each month, and the last day of each month.
January 1 – 66/45
January 15 – 68/46
January 31 – 69/47
February 1 – 69/47
February 15 – 71/49
February 28 – 73/51
February 29 – 73/51
March 1 – 74/52
March 15 – 78/54
March 31 – 82/57
April 1 – 82/58
April 15 – 85/60
April 30 – 89/65
May 1 – 89/65
May 15 – 94/69
May 31 – 100/74
June 1 – 100/74
June 15 – 104/78
June 30 – 107/83
July 1 – 107/83
July 15 – 107/85
July 31 – 106/85
August 1 – 106/85
August 15 – 105/84
August 31 – 104/82
September 1 – 104/82
September 15 – 101/79
September 30 – 96/73
October 1 – 95/72
October 15 – 90/66
October 31 – 83/60
November 1 – 83/59
November 15 – 77/54
November 30 – 70/48
December 1 – 69/48
December 15 – 66/45
December 31 – 66/45
SOURCE: www.weather.gov/psr/history.html
January Notes
Snow! Greatest potential for snow (as much as 20 inches can fall in a little more than 24 hours and greatest potential for the lowest temperatures of the year and all-time record lows. Snow cover can stay around for the entire month. Fog possible if a warm day occurs with snow on the ground. Days start getting longer around January 5, but nobody notices.
January 11-27 the normal low in Chicago hits and maintains the year’s lowest normal temperature of 16 F. Mid-January is the coldest part of the winter in Chicago. Record highs in January are in the 50’s and 60’s F. Record low ranges -9 to -27 F.