Joliet, Illinois climate: Normal weather by month, frost dates and records
Joliet's normal year runs from 17°F January nights to 84°F July afternoons, with 38.0 inches of precipitation and 17 inches of snow a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 10.2°C, January lows of −9°C, July highs of 29°C, 966 mm of precipitation a year.
- NOAA stationJoliet Brandon Rd Dam
- Station IDUSC00114530
- Location41.50°N 88.10°W
- Elevation543 ft (166 m)
- Population151,837
On October 14, the normal high in Joliet is 64°F and the normal low 44°F, and the chance of measurable rain or snow is 31%.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Joliet.
- Jan 31° 17°
- Feb 35° 20°
- Mar 47° 29°
- Apr 60° 39°
- May 71° 49°
- Jun 80° 60°
- Jul 84° 64°
- Aug 82° 63°
- Sep 76° 55°
- Oct 63° 43°
- Nov 49° 32°
- Dec 36° 22°
Each month: normal high (large) and low, °F. Fill: the month's normal mean, colder blue to hotter red.
What is the weather like in Joliet each month?
July is the warmest month, with normal highs of 84°F; January the coldest, with normal lows of 17°F. The most precipitation falls in July (4.55 in), the least in February (1.78 in).
Each month has its own page with the day-by-day normals, the month's records and its recent years:
| Month | High | Low | Mean | Precip. | Snow | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|---|
| January | 31°F | 17°F | 23.9°F | 1.99 | 5.0 | 11 | <1 | 28 | 9 h 30 min |
| February | 35°F | 20°F | 27.6°F | 1.78 | 6.2 | 9 | <1 | 25 | 10 h 40 min |
| March | 47°F | 29°F | 38.1°F | 2.27 | 2.1 | 10 | <1 | 21 | 11 h 50 min |
| April | 60°F | 39°F | 49.4°F | 3.93 | 0.1 | 12 | <1 | 6 | 13 h 20 min |
| May | 71°F | 49°F | 60.2°F | 4.53 | 0.0 | 12 | 1 | <1 | 14 h 30 min |
| June | 80°F | 60°F | 70.1°F | 4.30 | 0.0 | 11 | 4 | <1 | 15 h 10 min |
| July | 84°F | 64°F | 73.9°F | 4.55 | 0.0 | 9 | 6 | <1 | 14 h 50 min |
| August | 82°F | 63°F | 72.3°F | 3.97 | 0.0 | 9 | 3 | <1 | 13 h 50 min |
| September | 76°F | 55°F | 65.7°F | 3.17 | 0.0 | 8 | 2 | <1 | 12 h 30 min |
| October | 63°F | 43°F | 53.3°F | 3.14 | 0.0 | 10 | <1 | 3 | 11 h 10 min |
| November | 49°F | 32°F | 40.4°F | 2.46 | 0.3 | 10 | <1 | 16 | 9 h 50 min |
| December | 36°F | 22°F | 29.4°F | 1.94 | 3.2 | 11 | <1 | 26 | 9 h 10 min |
| Year (annual) | 60°F | 41°F | 50.4°F | 38.03 | 16.9 | 123 | 15 | 126 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. | Snow |
|---|---|---|---|---|---|
| January | 0°C | −9°C | −4.5°C | 51 mm | 13 cm |
| February | 2°C | −7°C | −2.4°C | 45 mm | 16 cm |
| March | 8°C | −2°C | 3.4°C | 58 mm | 5 cm |
| April | 16°C | 4°C | 9.7°C | 100 mm | 0 cm |
| May | 22°C | 10°C | 15.7°C | 115 mm | 0 cm |
| June | 27°C | 16°C | 21.2°C | 109 mm | 0 cm |
| July | 29°C | 18°C | 23.3°C | 116 mm | 0 cm |
| August | 28°C | 17°C | 22.4°C | 101 mm | 0 cm |
| September | 25°C | 13°C | 18.7°C | 81 mm | 0 cm |
| October | 17°C | 6°C | 11.8°C | 80 mm | 0 cm |
| November | 9°C | 0°C | 4.7°C | 62 mm | 1 cm |
| December | 2°C | −5°C | −1.4°C | 49 mm | 8 cm |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00114530; annual normals. Wet days: 0.01 inch or more; 90°F days and freezing nights: NOAA's day counts. Daylight: sunrise to sunset on the 15th, computed from the latitude.
When is the best weather to visit Joliet?
Normal highs sit between 65°F and 85°F in May, June, July, August and September. Of those, September has the fewest days with rain (8).
That is a measurement, not a recommendation: it counts the months whose normal afternoon high sits between 65°F and 85°F, where a light layer is enough by day.
Source: NOAA NCEI 1991-2020 monthly normals, station USC00114530.
When is the last frost in Joliet?
In Joliet, the last spring frost (32°F) comes after April 19 in half of years and after May 7 in one year in ten; the first autumn frost comes before October 25 in half of years and before October 12 in one year in ten.
Frost-free in half of yearsFrost in 1 to 9 years out of 10Frost most years
- Last spring frost, half of years after
- April 191 year in 10 after May 7; 9 in 10 after April 3
- First autumn frost, half of years before
- October 251 year in 10 before October 12; 9 in 10 before November 6
NOAA puts the median frost-free season at 188 days, and the season without a hard freeze (28°F) at 211 days.
A hard freeze (28°F) comes after April 5 in half of springs and before November 4 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Joliet in zones 5b to 6a across its 7 ZIP code areas (6a in 60436, the largest). By the map's own method, the average of each year's coldest night over 1991-2020, Joliet's NOAA station is in zone 6a: the coldest night of a typical year reaches −9°F (28 complete years).
Frost dates for every NOAA station in Illinois · Frost dates by ZIP code
Source: NOAA NCEI 1991-2020 annual normals (frost probabilities), station USC00114530; USDA 2023 Plant Hardiness Zone Map, ZIP listings: PRISM Group, Oregon State University, https://prism.oregonstate.edu, accessed October 8, 2026; the station zone: ACIS daily lows, 1991-2020. A 10% date means one year in ten has a frost after it in spring or before it in autumn.
What hardiness zone is each Joliet ZIP code in?
The USDA's 2023 map gives each ZIP code area one zone. Joliet's 7 ZIP code areas run from zone 5b to 6a: 2 in 5b and 5 in 6a. Each ZIP's frost dates are in the frost tool.
Source: USDA 2023 Plant Hardiness Zone Map, ZIP listings: PRISM Group, Oregon State University, https://prism.oregonstate.edu, accessed October 8, 2026; ZIP areas in the place: Census Bureau 2020 ZCTA-to-place relationship file. A ZIP area counts when at least a tenth of its land (and 0.5 km²) lies in the place.
How hot and how cold does it get in Joliet?
In a normal year in Joliet, 15 days a year reach 90°F, 126 nights fall to 32°F or colder and 123 days bring measurable precipitation.
- Days at 90°F or more
- 15a normal year
- Days at 100°F or more
- fewer than 1a normal year
- Nights at 32°F or colder
- 126a normal year
- Days that stay below freezing
- 43high of 32°F or less
- Days with 0.01 inch of precipitation
- 123a normal year
- Days with 1 inch of snow or more
- 7a normal year
The highest temperature in this station's record (since 1975) is 104°F, on June 26, 1988; the lowest is −26°F, on January 21, 1985.
The wettest calendar year on that record is 1993, with 47.08 in; the snowiest season is 2013–14, with 55.6 inches.
Source: NOAA NCEI 1991-2020 annual normals, station USC00114530; records: ACIS (NOAA Regional Climate Centers), station USC00114530. Records use complete months only; a month missing more than three days is left out.
How sunny is Joliet?
Over a year 73% of the sunlight that would reach the ground under clear skies gets through the clouds in the area around Joliet, 3.9 kWh per square metre a day. July is the sunniest month (81%) and January the cloudiest (61%). Among the 459 U.S. places of 50,000 or more, that ranks tied 352nd (with 32 others) in sunshine.
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 61% | 1.7 |
| February | 65% | 2.6 |
| March | 67% | 3.6 |
| April | 70% | 4.8 |
| May | 71% | 5.5 |
| June | 77% | 6.1 |
| July | 81% | 6.2 |
| August | 80% | 5.4 |
| September | 80% | 4.5 |
| October | 71% | 3.0 |
| November | 67% | 2.0 |
| December | 61% | 1.5 |
Source: NASA POWER solar climatology, 2001-2020 (CERES SYN1deg). Satellite-based, for the 1-degree cell (about 100 km across) around the station, so it describes the area rather than the airport.
How much heating and cooling does Joliet need?
A normal year in Joliet brings 6,171 heating degree days, 15% more than the median U.S. place (5,373), and 872 cooling degree days, 4% fewer than the median (908). Seven months need 300 or more heating degree days, a monthly mean of about 55°F or colder. For gardens and crops, NOAA counts 3,179 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 1,276 | 0 |
| February | 1,047 | 0 |
| March | 835 | 1 |
| April | 473 | 5 |
| May | 203 | 54 |
| June | 30 | 182 |
| July | 3 | 278 |
| August | 6 | 234 |
| September | 83 | 105 |
| October | 375 | 13 |
| November | 738 | 0 |
| December | 1,104 | 0 |
| Year (annual) | 6,171 | 872 |
Source: NOAA NCEI 1991-2020 monthly normals, station USC00114530. A degree day is one degree of a day's mean temperature below 65°F (heating) or above it (cooling); utilities use them to estimate energy use.
Has Joliet been warmer than normal lately?
2025 averaged 51.3°F, 0.9°F above the 1991-2020 normal of 50.4°F. 3 of the 3 complete years since 2023 ran warmer than the normal.
| Year | Mean | Against normal | Precip. | Snow |
|---|---|---|---|---|
| 2023 | 51.8°F | +1.4°F | 38.91 | 11.9 |
| 2024 | 53.1°F | +2.7°F | 36.44 | 16.3 |
| 2025 | 51.3°F | +0.9°F | 27.01 | 22.9 |
Over 43 complete years from 1978 to 2025, the station's annual mean temperature rose at a fitted 3.3°F per century (+0.18°C per decade). A fitted rate summarizes the whole record; single years swing well above and below it.
Source: observed years: ACIS, station USC00114530; trend: NOAA GHCN-Monthly v4. A year counts only with all twelve months complete.
How does Joliet's climate compare?
Joliet is warmer than 42 of the other 143 places with their own NOAA record in Illinois, and wetter than 32. Across the 7,247 U.S. stations with normals, its annual mean of 50.4°F is warmer than 42%.
In the Köppen classification computed from these normals, Joliet is Dfa: continental, no dry season, hot summer. What the classes mean.
Places with the most similar year elsewhere
Measured month by month on the normal high, low and precipitation, among places of 20,000 or more people in other states:
Source: NOAA NCEI 1991-2020 normals for every station PlainClimate covers. Similarity: the root-mean-square difference of the 36 monthly figures, precipitation weighted so an inch counts like 6°F.
Which places near Joliet share this climate record?
10 places have no NOAA station with 1991-2020 normals of their own, and this station is the nearest full record. A place's own climate can differ from these figures, by several degrees where it sits much higher or lower than the station, nearer the coast, or inside a large city's heat; for the larger places the next nearest records are named with their yearly mean, so the spread around them is visible, and places of 50,000 or more have their own page with NOAA's gridded normals.
- New Lenox, IL28,480 people · 7 mi E
- Shorewood, IL18,522 people · 6 mi W
- Manhattan, IL10,772 people · 9 mi SE
- Ridgewood, IL2,997 people · 4 mi NE
- Ingalls Park, IL2,970 people · 4 mi E
- Preston Heights, IL2,318 people · 1 mi SE
- Elwood, IL2,248 people · 6 mi S
- Rockdale, IL1,980 people · 1 mi W
- Wilton Center, IL141 people · 13 mi SE
- Symerton, IL124 people · 13 mi S
Source: Census Bureau 2024 Gazetteer (place centers) and Vintage 2024 population estimates. Distance and direction from the station to each place's center.
Questions about Joliet's climate
What is the coldest month in Joliet?
January, with a normal high of 31°F and a normal low of 17°F. The warmest is July (84°F by day, 64°F at night).
Does it snow in Joliet?
Yes: 17 inches in a normal year, falling on 12 days with 0.1 inch or more, the most in February (6.2 inches).
What is the rainiest month in Joliet?
July, with 4.55 in of precipitation in a normal year; the driest is February with 1.78 in.
What plant hardiness zone is Joliet in?
The USDA's 2023 map puts Joliet in zones 5b to 6a across its 7 ZIP code areas (6a in 60436, the largest). By the same method at Joliet's NOAA station, the coldest night of a typical year reaches −9°F (28 years, 1991-2020): zone 6a.
How late can frost come in Joliet?
In half of years the last 32°F night comes after April 19; in one year in ten it comes after May 7. Waiting until May 7 leaves about a one-in-ten chance of a later frost.
Nearby and next
- Joliet in OctoberThis month day by day, its records and recent years
- Illinois climateThe statewide normals and every place in the state
- Romeoville, IL7 miles from this station, 50.9°F a year
- Channahon, IL12 miles from this station, 51.1°F a year
- Little Red School House, IL19 miles from this station, 51.4°F a year
- Morris, IL19 miles from this station, 50.8°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made