Joliet, Illinois Weather
Fireflies rise from the lawn. Day 77 of spring. Read this microseason across nine climate regions →
Joliet weather forecast — hour by hour, 7-day outlook, NOAA radar
- TodayJun 4Overcast——86°58°—
- FridayJun 5Light Showers42%0.09″80°69°-6°
- SaturdayJun 6Light Showers72%—82°70°+2°
- SundayJun 7Showers27%0.01″82°69°0°
- MondayJun 8Light Showers48%0.08″74°68°-8°
- TuesdayJun 9Showers34%0.06″85°69°+11°
- WednesdayJun 10Thunderstorm26%0.01″86°70°+1°
Ozone at AQI 103 — peak already passed at 1 PM under clear skies. AQI up 21 in the last 6 hours — air quality is degrading. Levels should ease through evening.
CAUTION Sensitive groups (children, elderly, respiratory conditions) should limit prolonged outdoor exertion.
What's driving it
Ozone × UV × Sky
Ozone at AQI 103 — peak already passed at 1 PM under clear skies. Levels should ease through evening.
- Present
- AQI 103
- UV peak
- 5.5 at earlier today
- Sky at peak
- clear
- Projected peak
- AQI 103
Trends
Seven days of AQI and PM2.5.
Hourly air-quality data from the Copernicus Atmosphere Monitoring Service, charted across the past and next several days. Dashed lines mark the AQI breakpoints at 50 (Good → Moderate) and 100 (Moderate → Unhealthy for Sensitive Groups).
A summer fog for fair, a winter fog for rain.
- Moonrise
- 4:27 AM
- Moonset
- 1:49 PM
- In sign
- ♒︎ Aquarius
Fireflies rise from the lawn
Joliet at a glance
- Today vs. normal: 13°F above the seasonal normal for this latitude
- Last frost: April 25 (climatological average for this latitude)
- Microseason: Jun 1–5
- Planting window: Harvest spring lettuce before it bolts. Sow heat-tolerant greens.
Right now in the garden
Peak growing season
As of June 4, the growing season is at its peak — frost is months away. Continue succession-planting beans and summer squash. Start fall brassicas (broccoli, cabbage, kale) from seed indoors for transplanting in late summer.
SPC Convective Outlook
Storm Prediction Center — Joliet
SPC has placed Joliet in the Marginal Risk category for severe thunderstorms tomorrow.
- TODAYNONENo severe risk
- TOMORROWMRGLMarginal Risk
- DAY 3TSTMGeneral Thunderstorms
Isolated severe storms possible. Limited threat for hail or damaging wind.
Source: NOAA / NWS Storm Prediction Center categorical convective outlook. Outlooks are re-issued multiple times per day; this page reflects the most recent SPC polygons covering the city’s coordinates.
Planting calendar
| Month | Plant | Harvest |
|---|---|---|
| January | — | — |
| February | — | — |
| March | — | — |
| April | lettuce, peas, spinach, radishes | — |
| May | lettuce, peas, spinach, radishes, tomatoes, peppers, beans, squash | lettuce, peas, radishes |
| June | tomatoes, peppers, beans, squash | lettuce, peas, radishes |
| July | tomatoes, peppers, beans, squash | tomatoes, beans, summer squash |
| August | — | tomatoes, beans, summer squash |
| September | fall brassicas, garlic (overwinter), carrots | tomatoes, beans, summer squash |
| October | fall brassicas, garlic (overwinter), carrots | winter squash, tomatoes (last) |
| November | — | — |
| December | — | — |
A year in weather
July brings Joliet's warmest temperatures (~74°F mean) while January delivers the coldest (~24°F). Rainfall peaks in July (4.5 inches) and drops to its lowest point in February (1.8 inches).
| Month | Mean temp | Precip | Rainy days |
|---|---|---|---|
| January | 24° | 2.0″ | 5 |
| February | 28° | 1.8″ | 5 |
| March | 38° | 2.3″ | 5 |
| April | 49° | 3.9″ | 7 |
| May | 60° | 4.5″ | 8 |
| June | 70° | 4.3″ | 7 |
| July | 74° | 4.5″ | 6 |
| August | 72° | 4.0″ | 6 |
| September | 66° | 3.2″ | 5 |
| October | 53° | 3.1″ | 6 |
| November | 40° | 2.5″ | 5 |
| December | 29° | 1.9″ | 5 |
Regional context
Joliet belongs to a warm-summer humid continental climate region — sharing similar temperature ranges, seasonal patterns, and growing conditions with nearby cities in this climate group.
Similar climates: Chicago, IL, Rockford, IL, Round Lake Beach, IL, Aurora, IL, Naperville, IL.
Naturalist notes
Late April brings the first migrating warblers through Joliet's woodlands as oak trees begin leafing out.
May nights fill with the territorial calls of American toads as lilac bushes reach peak bloom across the city.
Frequently asked
- When does it freeze in Joliet?
- Joliet's last spring frost typically falls around mid-April, and the first fall frost arrives around mid-November.
- What is the rainy season in Joliet?
- July is the wettest month with about 4.5 inches of rain on average; the city receives roughly 38 inches annually.
- What is the warmest month in Joliet?
- July is typically warmest, averaging about 74°F.
- What is the coldest month in Joliet?
- January is typically coldest, averaging about 24°F.
- When can I start a vegetable garden in Joliet?
- Cool-season crops (peas, lettuce) can be sown around the last spring frost (mid-April); warm-season crops (tomatoes, peppers) wait until 1–2 weeks after.
- How many rainy days does Joliet get?
- Joliet averages about 70 rainy days per year.
- What hardiness zone is Joliet?
- Joliet's USDA hardiness zone is determined by its lowest average winter temperature; check the USDA's online lookup with the city ZIP for the current zone designation.
Climate
Joliet, Illinois sits in a warm-summer humid continental climate zone. January temperatures hover near 24°F while July averages 74°F — a 50°F seasonal swing.
Throughout the year, Joliet receives about 38 inches of precipitation spread over roughly 70 rainy days.
Latitude (41.5°N), proximity to large water bodies, and elevation set the rhythm of the year — shaping what grows here, when frost is likely, and what the weather story looks like day to day.