Weather in Summit, Illinois
Roses open along the stoops. Day 59 of spring. Read this microseason across nine climate regions →
- TodayMay 16Light Rain53%83°64°
- SundayMay 17Overcast14%87°63°
- MondayMay 18Showers62%79°70°
- TuesdayMay 19Light Showers68%77°58°
- WednesdayMay 20Overcast21%60°48°
- ThursdayMay 21Overcast—64°48°
- FridayMay 22Overcast11%59°53°
- PM 2.5
- 7.9 μg/m³
- PM 10
- 9.0 μg/m³
- NO₂
- 11.9 μg/m³
- Ozone
- 79.0 μg/m³
- UV Index
- 0.0 Low
When the dew is on the grass, rain will never come to pass.
- Moonrise
- 10:34 AM
- Moonset
- 1:36 AM
- In sign
- ♊︎ Gemini
Roses open along the stoops
Summit at a glance
- Today vs. normal: 3°F below the seasonal normal for this latitude
- Last frost: April 27 (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
Summit's warmest month is July (~76°F mean) and its coldest is January (~26°F). Rainfall peaks in May (4.1 inches) and bottoms out in February (1.5 inches).
| Month | Mean temp | Precip | Rainy days |
|---|---|---|---|
| January | 26° | 1.5″ | 3 |
| February | 30° | 1.5″ | 3 |
| March | 40° | 1.9″ | 5 |
| April | 51° | 3.6″ | 7 |
| May | 62° | 4.1″ | 8 |
| June | 72° | 4.0″ | 8 |
| July | 76° | 3.5″ | 6 |
| August | 75° | 4.0″ | 6 |
| September | 68° | 2.8″ | 5 |
| October | 55° | 3.5″ | 6 |
| November | 42° | 2.4″ | 5 |
| December | 31° | 1.8″ | 4 |
Regional context
Summit sits within a warm-summer humid continental climate region — a cohort that shares similar temperature ranges, seasonal patterns, and growing conditions across nearby cities.
Similar climates: Chicago, IL, Rockford, IL, Round Lake Beach, IL, Aurora, IL, Naperville, IL.
Frequently asked
- When does it freeze in Summit?
- Summit's last spring frost typically falls around mid-April, and the first fall frost arrives around mid-November.
- What is the rainy season in Summit?
- May is the wettest month with about 4.1 inches of rain on average; the city receives roughly 34 inches annually.
- What is the warmest month in Summit?
- July is typically warmest, averaging about 76°F.
- What is the coldest month in Summit?
- January is typically coldest, averaging about 26°F.
- When can I start a vegetable garden in Summit?
- 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 Summit get?
- Summit averages about 68 rainy days per year.
- What hardiness zone is Summit?
- Summit'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
Summit, Illinois sits in a warm-summer humid continental climate zone. January means hover near 26°F while July averages 76°F — a 50°F seasonal swing.
Across the year, Summit receives about 34 inches of precipitation spread over roughly 68 rainy days.
The rhythm of the year is set by latitude (41.8°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.