Washington, Illinois Weather
Fireflies pulse through the magnolias. Day 76 of spring. Read this microseason across nine climate regions →
Washington weather forecast — hour by hour, 7-day outlook, NOAA radar
- TodayJun 3Overcast——81°51°—
- ThursdayJun 4Overcast——83°56°+2°
- FridayJun 5Drizzle57%—81°65°-2°
- SaturdayJun 6Showers57%—81°67°0°
- SundayJun 7Light Drizzle34%—85°65°+4°
- MondayJun 8Showers43%—78°68°-7°
- TuesdayJun 9Light Drizzle29%0.01″77°70°-1°
Ozone at AQI 78 — peak already passed at 1 PM under overcast skies. AQI up 16 in the last 6 hours — air quality is degrading. Levels should ease through evening.
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 78 — peak already passed at 1 PM under overcast skies. Levels should ease through evening.
- Present
- AQI 78
- UV peak
- 5.9 at earlier today
- Sky at peak
- overcast
- Projected peak
- AQI 78
PM × Wind × Precip
PM2.5 at 6.3 µg/m³, PM10 at 7.9 µg/m³ — typical background levels with no transport signature.
- PM2.5/PM10
- 0.80
- Wind
- light
- 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
- 3:52 AM
- Moonset
- 12:54 PM
- In sign
- ♑︎ Capricorn
Fireflies pulse through the magnolias
Washington at a glance
- Today vs. normal: 7°F above the seasonal normal for this latitude
- Last frost: April 20 (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 — Washington
SPC has placed Washington 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
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.