Weather in Washington, Illinois
Roses open on the Piedmont edge. Day 59 of spring. Read this microseason across nine climate regions →
- TodayMay 16Overcast44%78°61°
- SundayMay 17Overcast24%85°65°
- MondayMay 18Heavy Rain76%78°66°
- TuesdayMay 19Light Showers68%75°56°
- WednesdayMay 20Overcast14%64°46°
- ThursdayMay 21Overcast—63°45°
- FridayMay 22Overcast11%60°53°
- PM 2.5
- 9.3 μg/m³
- PM 10
- 10.8 μg/m³
- NO₂
- 19.6 μg/m³
- Ozone
- 49.0 μg/m³
- UV Index
- 0.0 Low
When the dew is on the grass, rain will never come to pass.
- Moonrise
- 10:44 AM
- Moonset
- 1:39 AM
- In sign
- ♊︎ Gemini
Roses open on the Piedmont edge
Washington at a glance
- Today vs. normal: 4°F below the seasonal normal for this latitude
- Last frost: April 20 (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
Washington's warmest month is July (~76°F mean) and its coldest is January (~26°F). Rainfall peaks in May (4.7 inches) and bottoms out in February (2.0 inches).
| Month | Mean temp | Precip | Rainy days |
|---|---|---|---|
| January | 26° | 2.1″ | 5 |
| February | 30° | 2.0″ | 5 |
| March | 41° | 2.7″ | 6 |
| April | 53° | 4.0″ | 8 |
| May | 64° | 4.7″ | 8 |
| June | 73° | 3.7″ | 7 |
| July | 76° | 3.5″ | 5 |
| August | 75° | 3.3″ | 6 |
| September | 67° | 3.5″ | 5 |
| October | 55° | 3.2″ | 6 |
| November | 42° | 2.7″ | 6 |
| December | 31° | 2.2″ | 5 |
Regional context
Washington 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 Washington?
- Washington's last spring frost typically falls around mid-April, and the first fall frost arrives around mid-November.
- What is the rainy season in Washington?
- May is the wettest month with about 4.7 inches of rain on average; the city receives roughly 38 inches annually.
- What is the warmest month in Washington?
- July is typically warmest, averaging about 76°F.
- What is the coldest month in Washington?
- January is typically coldest, averaging about 26°F.
- When can I start a vegetable garden in Washington?
- 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 Washington get?
- Washington averages about 71 rainy days per year.
- What hardiness zone is Washington?
- Washington'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
Washington, Illinois sits in a humid subtropical climate zone. January means hover near 26°F while July averages 76°F — a 51°F seasonal swing.
Across the year, Washington receives about 38 inches of precipitation spread over roughly 71 rainy days.
The rhythm of the year is set by latitude (40.7°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.