Joliet, Illinois Weather
Fireflies rise from the lawn. Day 78 of spring. Read this microseason across nine climate regions →
Joliet weather forecast — hour by hour, 7-day outlook, NOAA radar
- TodayJun 4Overcast——87°58°—
- FridayJun 5Light Rain45%0.11″83°68°-4°
- SaturdayJun 6Heavy Drizzle32%—88°69°+5°
- SundayJun 7Light Showers31%—81°69°-7°
- MondayJun 8Heavy Drizzle72%0.02″73°69°-8°
- TuesdayJun 9Light Showers54%0.08″86°70°+13°
- WednesdayJun 10Thunderstorm37%0.22″87°72°+1°
AQI 74 (Moderate), driven by PM2.5. AQI down 5 over the last 6 hours (steady decline since this morning). PM2.5 at 9.1 µg/m³, PM10 at 10.2 µg/m³ — typical background levels with no transport signature.
OK No precautions needed for the general population; unusually sensitive individuals may consider limiting prolonged outdoor exertion.
What's driving it
Ozone × UV × Sky
Ozone at AQI 39. Overcast through the UV peak window (cloud cover ~100%) — afternoon ozone should stay flat.
- Present
- AQI 39
- UV peak
- 0.0 at 1 PM
- Sky at peak
- overcast
- Projected peak
- AQI 5
PM × Wind × Precip
PM2.5 at 9.1 µg/m³, PM10 at 10.2 µg/m³ — typical background levels with no transport signature.
- PM2.5/PM10
- 0.89
- Wind
- breezy
- Recent rain
- 0h in last 6h
- Pattern
- background
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).
The higher the clouds, the finer the weather.
- Moonrise
- 4:56 AM
- Moonset
- 2:56 PM
- In sign
- ♒︎ Aquarius
Fireflies rise from the lawn
Joliet at a glance
- Today vs. normal: 75°F — typical for the season
- 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 5, 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.
- TODAYTSTMGeneral Thunderstorms
- 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.