Granite City, Illinois Weather
Fireflies pulse through the magnolias. Day 76 of spring. Read this microseason across nine climate regions →
Granite City weather forecast — hour by hour, 7-day outlook, NOAA radar
- TodayJun 3Mostly Clear——83°54°—
- ThursdayJun 4Overcast——86°60°+3°
- FridayJun 5Light Drizzle26%—86°66°0°
- SaturdayJun 6Showers34%—91°67°+5°
- SundayJun 7Light Showers34%—90°73°-1°
- MondayJun 8Light Drizzle56%—83°72°-7°
- TuesdayJun 9Drizzle32%0.04″84°71°+1°
Ozone at AQI 91 now. AQI up 13 over the last 6 hours (gradual rise). With UV 8.3 peaking around 1 PM under clear skies, surface ozone likely climbs to AQI 101 by mid-afternoon.
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 91 now. With UV 8.3 peaking around 1 PM under clear skies, surface ozone likely climbs to AQI 101 by mid-afternoon.
- Present
- AQI 91
- UV peak
- 8.3 at 1 PM
- Sky at peak
- clear
- Projected peak
- AQI 101
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
- 3:48 AM
- Moonset
- 1:04 PM
- In sign
- ♑︎ Capricorn
Fireflies pulse through the magnolias
Granite City at a glance
- Today vs. normal: 5°F above the seasonal normal for this latitude
- Last frost: April 8 (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 3, 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 — Granite City
SPC has placed Granite City in the General Thunderstorms category for severe thunderstorms day after tomorrow.
- TODAYNONENo severe risk
- TOMORROWNONENo severe risk
- DAY 3TSTMGeneral Thunderstorms
Thunderstorms possible. Not severe, but capable of producing lightning and brief heavy rain.
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
Granite City's warmest month is July (~81°F mean) and its coldest is January (~33°F). Rainfall peaks in May (4.9 inches) and bottoms out in February (2.3 inches).
| Month | Mean temp | Precip | Rainy days |
|---|---|---|---|
| January | 33° | 2.7″ | 9 |
| February | 37° | 2.3″ | 8 |
| March | 47° | 3.6″ | 12 |
| April | 58° | 4.8″ | 16 |
| May | 68° | 4.9″ | 16 |
| June | 77° | 4.7″ | 16 |
| July | 81° | 4.2″ | 14 |
| August | 79° | 3.8″ | 13 |
| September | 72° | 3.4″ | 11 |
| October | 60° | 3.2″ | 11 |
| November | 48° | 3.7″ | 12 |
| December | 37° | 2.6″ | 9 |
Regional context
Granite City sits within a humid subtropical climate region — a cohort that shares similar temperature ranges, seasonal patterns, and growing conditions across nearby cities.
Similar climates: Peoria, IL, Springfield, IL, Champaign, IL, Bloomington, IL, Alton, IL.
Frequently asked
- When does it freeze in Granite City?
- Granite City's last spring frost typically falls around mid-April, and the first fall frost arrives around mid-November.
- What is the rainy season in Granite City?
- May is the wettest month with about 4.9 inches of rain on average; the city receives roughly 44 inches annually.
- What is the warmest month in Granite City?
- July is typically warmest, averaging about 81°F.
- What is the coldest month in Granite City?
- January is typically coldest, averaging about 33°F.
- When can I start a vegetable garden in Granite City?
- 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 Granite City get?
- Granite City averages about 147 rainy days per year.
- What hardiness zone is Granite City?
- Granite City'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
Granite City, Illinois sits in a humid subtropical climate zone. January means hover near 33°F while July averages 81°F — a 48°F seasonal swing.
Across the year, Granite City receives about 44 inches of precipitation spread over roughly 147 rainy days.
The rhythm of the year is set by latitude (38.7°N), proximity to large water bodies, and elevation — all of which shape what grows here, when frost is likely, and what the weather story looks like day to day.