Weather in Granite City, Illinois
Roses open on the Piedmont edge. Day 59 of spring. Read this microseason across nine climate regions →
- TodayMay 16Showers62%78°71°
- SundayMay 17Overcast—87°67°
- MondayMay 18Showers49%80°70°
- TuesdayMay 19Showers91%81°61°
- WednesdayMay 20Overcast72%68°53°
- ThursdayMay 21Light Drizzle15%64°53°
- FridayMay 22Light Drizzle17%65°55°
- PM 2.5
- 6.7 μg/m³
- PM 10
- 7.3 μg/m³
- NO₂
- 10.3 μg/m³
- Ozone
- 65.0 μg/m³
- UV Index
- 0.0 Low
When the dew is on the grass, rain will never come to pass.
- Moonrise
- 10:54 AM
- Moonset
- 1:35 AM
- In sign
- ♊︎ Gemini
Roses open on the Piedmont edge
Granite City at a glance
- Today vs. normal: 72°F — typical for the season
- Last frost: April 8 (climatological average for this latitude)
- Microseason: 28 of 72, May 16–20
- Planting window: Direct sow okra, melons, and southern peas. Thin carrot rows.
Right now in the garden
Warm-season window is open
As of May 17, the last spring frost has passed for most years. Transplant tomatoes, peppers, eggplants, basil, and cucurbits (cucumbers, squash, melons) now. Direct-sow beans and corn into warm soil.
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.