Climateby Month

Joliet, IL climate by month

NOAA 1991-2020 normals · 541 ft elevation

Joliet has warm and often humid summers and cold winters. Highs peak at 84°F in July and fall to 31°F in January. Wet days are spread through the year, from about 8 to 12 a month. Normal snowfall is about 17 in a year. By our comfort score the best month is May.

Warmest month
84°F
July normal high
Coldest month
17°F
January normal low
Wet days a year
123
38.0 in of precipitation
Snow a year
16.9 in
normal snowfall

How warm is Joliet?

Normal highs range from 31°F in January to 84°F in July.

0°20°40°60°80°100° January: normal high 31°F (-1°C), low 17°F (-8°C) 31° 17° February: normal high 35°F (2°C), low 20°F (-7°C) March: normal high 47°F (8°C), low 29°F (-2°C) April: normal high 60°F (16°C), low 39°F (4°C) May: normal high 71°F (22°C), low 49°F (9°C) June: normal high 80°F (27°C), low 60°F (16°C) July: normal high 84°F (29°C), low 64°F (18°C) 84° 64° August: normal high 82°F (28°C), low 63°F (17°C) September: normal high 76°F (24°C), low 55°F (13°C) October: normal high 63°F (17°C), low 43°F (6°C) November: normal high 49°F (9°C), low 32°F (0°C) December: normal high 36°F (2°C), low 22°F (-6°C) JFMAMJJASOND

Bars run from the normal low to the normal high for each month.

How rainy is Joliet?

May has the most wet days (about 12); the year brings about 38 in of precipitation.

January: 11 wet days February: 9 wet days March: 10 wet days April: 12 wet days May: 12 wet days 12 June: 11 wet days July: 9 wet days August: 9 wet days September: 8 wet days 8 October: 10 wet days November: 10 wet days December: 11 wet days JFMAMJJASOND

Wet day: at least 0.01 in of rain or melted snow, counted from daily records 1991-2020.

How much does it snow?

Normal snowfall is 16.9 in a year, most of it in February.

January: 5.0 in of snow February: 6.2 in of snow 6.2 March: 2.1 in of snow April: 0.1 in of snow May: 0.0 in of snow 0.0 June: 0.0 in of snow July: 0.0 in of snow August: 0.0 in of snow September: 0.0 in of snow October: 0.0 in of snow November: 0.3 in of snow December: 3.2 in of snow JFMAMJJASOND

How humid is Joliet?

Muggy days peak in July, at about 12 days.

January: 0 muggy days 0 February: 0 muggy days March: 0 muggy days April: 0 muggy days May: 1 muggy days June: 6 muggy days July: 12 muggy days 12 August: 11 muggy days September: 3 muggy days October: 0 muggy days November: 0 muggy days December: 0 muggy days JFMAMJJASOND

Muggy day: daily mean dew point of 65°F or higher, from hourly observations 1991-2020 at Chicago Midway Intl Arpt, 25 mi NE of the city center (the nearest airport with complete hourly records).

How much daylight?

Daylight ranges from about 9.2 hours in December to 15.1 hours in June.

January: 9.6 hours of daylight February: 10.6 hours of daylight March: 12.0 hours of daylight April: 13.3 hours of daylight May: 14.5 hours of daylight June: 15.1 hours of daylight 15.1 July: 14.8 hours of daylight August: 13.8 hours of daylight September: 12.5 hours of daylight October: 11.1 hours of daylight November: 9.9 hours of daylight December: 9.2 hours of daylight 9.2 JFMAMJJASOND
See all numbers
Monthly climate normals and day counts for Joliet, 1991-2020
MonthHighLowPrecip.Wet daysSnowMuggy daysDaylight
January 31°F17°F 2.0 in11 5.0 in 0 9.6 h
February 35°F20°F 1.8 in9 6.2 in 0 10.6 h
March 47°F29°F 2.3 in10 2.1 in 0 12.0 h
April 60°F39°F 3.9 in12 0.1 in 0 13.3 h
May 71°F49°F 4.5 in12 0.0 in 1 14.5 h
June 80°F60°F 4.3 in11 0.0 in 6 15.1 h
July 84°F64°F 4.5 in9 0.0 in 12 14.8 h
August 82°F63°F 4.0 in9 0.0 in 11 13.8 h
September 76°F55°F 3.2 in8 0.0 in 3 12.5 h
October 63°F43°F 3.1 in10 0.0 in 0 11.1 h
November 49°F32°F 2.5 in10 0.3 in 0 9.9 h
December 36°F22°F 1.9 in11 3.2 in 0 9.2 h

High and low: NOAA 1991-2020 normal daily high and low. Wet days: at least 0.01 in of rain or melted snow. Muggy days: daily mean dew point 65°F or higher.

Best months to visit Joliet

By our comfort score, the best month is May.

Comfort score by month (0-100) and its parts, in days per month
MonthScoreComfortableNotable rainHot or cold
Jan 270524
Feb 320519
Mar 46359
Apr 621071
May 711581
Jun 641074
Jul 58666
Aug 59763
Sep 671452
Oct 611260
Nov 42357
Dec 290520

Score = 40 × share of comfortable days + 25 × share of days without notable rain + 20 × share of days neither hot (90°F+) nor cold (high 40°F or below) + 15 × daylight. How the score works.

Frost dates in Joliet

The last spring frost typically comes around Apr 19, and the first fall frost around Oct 25, leaving 188 frost-free days in a typical year.

Frost and freeze dates for Joliet
Typical date1 year in 10
Last spring frost (32°F)Apr 19after May 7
First fall frost (32°F)Oct 25before Oct 12
Last hard freeze (28°F)Apr 5after Apr 21
First hard freeze (28°F)Nov 4before Oct 23
Frost-free season188 daysunder 167 days

"Typical" is the date with a 50% chance of a later spring frost (or earlier fall frost). Planting after the "1 year in 10" spring date gives a 90% chance of no further frost. The Old Farmer's Almanac publishes 30% dates, which fall between our typical and 1-in-10 dates.

Station: Joliet Brandon Rd Dam (USC00114530), NOAA 1991-2020 freeze probabilities. Frost dates for every city in Illinois.

Hottest and coldest readings, 1991-2020

The highest reading was 103°F (July 14, 1995); the lowest was -22°F (January 31, 2019, and 1 other day).

From the temperature station's daily records with NOAA quality flags removed. Not an all-time record.

Near Joliet

Similar climates elsewhere

Where the numbers come from

  • Temperature, rain, snowfall, snow depth and frost dates: Joliet Brandon Rd Dam (USC00114530), 1.9 mi SW of the city center, 543 ft . NOAA normals and daily records, 1991-2020.
  • Humidity and wind by hour: Chicago Midway Airport (USW00014819), 25 mi NE of the city center, 612 ft (71 ft higher than the city). NOAA normals and daily records, 1991-2020.
  • Daily humidity and wind: Chicago Midway Intl Arpt (725340-14819), 25 mi NE of the city center, 610 ft (69 ft higher than the city). Hourly observations, 1991-2020.
  • Not available for this location: cloud cover (no station close enough or similar enough in elevation).

Distances from the city center (USGS). Methodology · Report an error