Joliet climate
Joliet (Illinois, United States) has a hot-summer humid continental climate (Köppen Dfa). The average temperature over the year is 10 °C51 °F, and about 985 mm39 in of precipitation falls in an average year.
Temperature by month
Precipitation by month
Joliet climate table
| Month | High °C°F | Low °C°F | Mean °C°F | Precip. mmin | Frost days |
|---|---|---|---|---|---|
| Jan | 031 | −916 | −524 | 481.9 | 29 |
| Feb | 235 | −818 | −326 | 512.0 | 27 |
| Mar | 948 | −228 | 338 | 632.5 | 22 |
| Apr | 1661 | 439 | 1050 | 963.8 | 8 |
| May | 2272 | 1050 | 1661 | 1174.6 | 0 |
| Jun | 2781 | 1660 | 2170 | 1134.5 | 0 |
| Jul | 2984 | 1865 | 2475 | 1004.0 | 0 |
| Aug | 2883 | 1763 | 2373 | 1054.1 | 0 |
| Sep | 2577 | 1355 | 1966 | 853.3 | 0 |
| Oct | 1763 | 642 | 1153 | 893.5 | 3 |
| Nov | 949 | 031 | 540 | 602.4 | 17 |
| Dec | 236 | −622 | −229 | 572.2 | 27 |
| Year | 2984 | −916 | 1051 | 98539 | 134 |
“Year” row: highest monthly high, lowest monthly low, annual mean and annual total. Frost days are for the whole grid cell.
| Month | Humid. | Cloud | Solar | Daylight |
|---|---|---|---|---|
| Jan | 85% | 68% | 1.7 | 9:29 |
| Feb | 83% | 67% | 2.6 | 10:33 |
| Mar | 79% | 64% | 3.6 | 11:49 |
| Apr | 75% | 61% | 4.7 | 13:17 |
| May | 76% | 62% | 5.5 | 14:30 |
| Jun | 77% | 55% | 6.1 | 15:10 |
| Jul | 75% | 48% | 6.2 | 14:54 |
| Aug | 74% | 47% | 5.4 | 13:50 |
| Sep | 74% | 44% | 4.5 | 12:25 |
| Oct | 75% | 57% | 3.0 | 11:00 |
| Nov | 79% | 62% | 2.0 | 9:47 |
| Dec | 86% | 70% | 1.5 | 9:11 |
Humid. = average relative humidity at 2 m; cloud = average cloud amount; solar = average daily solar energy reaching the ground in kWh/m² (all-sky); daylight in hours:minutes, calculated for the 15th of each month.
What the climate of Joliet is like
The warmest month is July, with an average high of 29 °C84 °F and a low of 18 °C65 °F. The coldest is January, when highs average 0 °C31 °F and lows −9 °C16 °F. Seasons are strongly marked: the warmest month is on average 28.3 °C51 °F warmer than the coldest.
Annual precipitation is moderate at about 985 mm39 in. The wettest three-month stretch is May–July, which brings 34% of the annual total. The wettest month is May (117 mm4.6 in), the driest is January (48 mm1.9 in).
Relative humidity ranges from 74% in September to 86% in December. The clearest skies (lowest average cloud amount, 44%) are typical of September. Average wind speed near the ground ranges from 8 km/h (5 mph) in August to 14 km/h (9 mph) in April. Daylight lasts from about 9.2 hours in December to 15.2 hours in June.
A lasting snow cover is typical in December–February, when the average snow depth in the reanalysis exceeds 10 cm (deepest in January, about 16 cm).
Best time to visit Joliet
Based on these averages, the most comfortable months for sightseeing and outdoor activities are September: average highs of 25 °C77 °F to 25 °C77 °F with 85 mm3.3 in to 85 mm3.3 in of precipitation per month.
The most challenging month is January, which is cold, with average highs of 0 °C31 °F.
Comfort score: months are ranked by how close they come to an average high of 21–28 °C (70–82 °F), lows above 5 °C (41 °F), little precipitation and moderate humidity. The best-ranked months of each place are recommended, even where none meets all of these. These are general rules of thumb applied to long-term averages.
What to pack for Joliet
- Winter (December–February) — highs 031 to 2 °C36 °F, lows −916 to −6 °C22 °F, about 52 mm2.0 in of precipitation a month. Pack a winter coat, hat, gloves and warm, non-slip boots and shoes with good grip, as frost is common.
- Spring (March–May) — highs 948 to 22 °C72 °F, lows −228 to 10 °C50 °F, about 92 mm3.6 in of precipitation a month. Pack long sleeves, a sweater and a medium jacket, an extra layer for the cooler mornings and evenings and an umbrella or light rain jacket.
- Summer (June–August) — highs 2781 to 29 °C84 °F, lows 1660 to 18 °C65 °F, about 106 mm4.2 in of precipitation a month. Pack light summer clothes such as T-shirts, shorts or light dresses, an extra layer for the cooler mornings and evenings and an umbrella or light rain jacket.
- Autumn (September–November) — highs 949 to 25 °C77 °F, lows 031 to 13 °C55 °F, about 78 mm3.1 in of precipitation a month. Pack long sleeves, a sweater and a medium jacket and an extra layer for the cooler mornings and evenings.
How Joliet compares
Compared with Aurora, about 33 km to the northwest, Joliet is on average 0.6 °C1.1 °F warmer and receives a similar amount of precipitation. The difference is largest in April (1.1 °C2 °F warmer).
Of the 222 places in the United States covered by World Climates, Joliet is the 194th warmest by annual mean temperature and the 107th wettest by annual precipitation. See all of them on the United States climate page.
Places in other countries with the most similar temperature and rainfall pattern: Windsor (Canada, Dfa), Baia Mare (Romania, Dfa) and Uzhhorod (Ukraine, Dfb).
Nearby places
- Aurora 33 km · 10 °C49 °F · 983 mm39 in
- Chicago 51 km · 10 °C50 °F · 982 mm39 in
- Elgin 59 km · 10 °C49 °F · 983 mm39 in
- Rockford 118 km · 9 °C48 °F · 967 mm38 in
- South Bend 153 km · 10 °C50 °F · 994 mm39 in
- Peoria 156 km · 11 °C52 °F · 983 mm39 in
- Milwaukee 169 km · 9 °C48 °F · 945 mm37 in
- Madison 203 km · 8 °C47 °F · 970 mm38 in
Frequently asked questions
What is the warmest month in Joliet?
July is the warmest month in Joliet, with an average high of 29 °C (84 °F) and an average low of 18 °C (65 °F).
What is the coldest month in Joliet?
January is the coldest month, with an average high of 0 °C (31 °F) and an average low of -9 °C (16 °F).
When does it rain the most in Joliet?
May is the wettest month with about 117 mm (4.6 in) of precipitation; January is the driest with about 48 mm (1.9 in).
What is the best time to visit Joliet?
Judging by long-term averages, the most comfortable months are September.
About this data
All figures are 25-year averages (January 2001 – December 2025) from the NASA POWER project. Temperature, humidity, wind and precipitation come from the MERRA-2 reanalysis (precipitation is the bias-corrected MERRA-2 product), cloud and solar values from CERES satellite data. They describe a grid cell of roughly 50–70 km, not a single weather station, so they can differ from airport records — most of all on coasts, in mountains and for rainfall. Average highs and lows are the monthly mean temperature plus/minus half of the average daily temperature range. Counts of rainy days are not part of this dataset.