River Forest, Illinois Weather
Fireflies rise from the lawn. Day 77 of spring. Read this microseason across nine climate regions →
River Forest weather forecast — hour by hour, 7-day outlook, NOAA radar
- TodayJun 4Overcast——88°60°—
- FridayJun 5Light Showers45%0.13″79°69°-9°
- SaturdayJun 6Drizzle55%—86°67°+7°
- SundayJun 7Showers16%—81°66°-5°
- MondayJun 8Light Showers39%0.20″70°66°-11°
- TuesdayJun 9Light Showers34%—89°68°+19°
- WednesdayJun 10Heavy Drizzle25%—90°70°+1°
Ozone at AQI 119. AQI up 5 over the last 6 hours (gradual rise). Overcast through the UV peak window (cloud cover ~67%) — afternoon ozone should stay flat.
CAUTION Sensitive groups (children, elderly, respiratory conditions) should limit prolonged outdoor exertion.
What's driving it
Ozone × UV × Sky
Ozone at AQI 119. Overcast through the UV peak window (cloud cover ~67%) — afternoon ozone should stay flat.
- Present
- AQI 119
- UV peak
- 7.2 at 1 PM
- Sky at peak
- overcast
- Projected peak
- AQI 57
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).
A summer fog for fair, a winter fog for rain.
- Moonrise
- 4:27 AM
- Moonset
- 1:47 PM
- In sign
- ♒︎ Aquarius
Fireflies rise from the lawn
River Forest at a glance
- Today vs. normal: 13°F above the seasonal normal for this latitude
- Last frost: April 27 (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 4, 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 — River Forest
SPC has placed River Forest in the Marginal Risk category for severe thunderstorms tomorrow.
- TODAYNONENo severe risk
- TOMORROWMRGLMarginal Risk
- DAY 3TSTMGeneral Thunderstorms
Isolated severe storms possible. Limited threat for hail or damaging wind.
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
River Forest'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
River Forest's baseline climate, derived from NOAA NCEI 1991-2020 normals at the nearest reporting station, swings from a January mean of 26°F to a July mean of 76°F — a 50°F seasonal arc typical of the mid-latitude bands. Annual precipitation runs about 34.4 inches spread across roughly 68 days with measurable rain or snow each year.
Precipitation runs summer-dominant here: May averages 4.1 inches across 8.2 days with measurable rain, driven mostly by warm-season storms and thunderstorm activity, while February drops to just 1.5 inches across 3.4 rainy days under drier cool-season air. That wet-warm-summer pattern groups River Forest with places like Oak Park, IL, Maywood, IL and Forest Park, IL — a regional cohort where summer thunderstorm season carries more than half the annual moisture.
The frost-sensitive growing window opens around mid-April, when overnight lows reliably clear freezing for cool-season crops like kale, peas, spinach, and parsnips. Warm-season transplants — tomatoes, peppers, and basil — typically wait two weeks past that date to avoid late spring cold snaps. The window closes around mid-November, when overnight lows resume dipping below freezing and frost-tender plants need protection or harvest. These dates represent 30-year central tendencies; actual year-to-year variation can shift either bookend by 7-14 days, and local microclimate features within River Forest — cold-air drainage on calm clear nights, slope aspect, distance from any nearby lake or river — can push the practical frost window earlier or later than the regional average.
Similar climates: Oak Park, IL, Maywood, IL, Forest Park, IL, Elmwood Park, IL, River Grove, IL.
Frequently asked
- When does it freeze in River Forest?
- River Forest's last spring frost typically falls around mid-April, and the first fall frost arrives around mid-November.
- What is the rainy season in River Forest?
- 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 River Forest?
- July is typically warmest, averaging about 76°F.
- What is the coldest month in River Forest?
- January is typically coldest, averaging about 26°F.
- When can I start a vegetable garden in River Forest?
- 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 River Forest get?
- River Forest averages about 68 rainy days per year.
- What hardiness zone is River Forest?
- River Forest'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
River Forest, 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, River Forest receives about 34 inches of precipitation spread over roughly 68 rainy days.
The rhythm of the year is set by latitude (41.9°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.