Princeton, Illinois Weather
Fireflies rise from the lawn. Day 76 of spring. Read this microseason across nine climate regions →
Princeton weather forecast — hour by hour, 7-day outlook, NOAA radar
- TodayJun 3Overcast——81°51°—
- ThursdayJun 4Overcast——84°57°+3°
- FridayJun 5Light Drizzle63%—80°68°-4°
- SaturdayJun 6Showers63%0.76″82°64°+2°
- SundayJun 7Overcast20%—82°64°0°
- MondayJun 8Light Showers33%0.02″74°66°-8°
- TuesdayJun 9Drizzle26%0.03″78°69°+4°
Ozone at AQI 75 — peak already passed at 1 PM under partly cloudy skies. AQI up 15 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 75 — peak already passed at 1 PM under partly cloudy skies. Levels should ease through evening.
- Present
- AQI 75
- UV peak
- 5.7 at earlier today
- Sky at peak
- partly cloudy
- Projected peak
- AQI 75
PM × Wind × Precip
PM2.5 at 6.2 µg/m³ (AQI 34) with a 0.78 fine-to-coarse ratio and 5 mph wind — combustion smoke trapped in calm air, not road dust.
- PM2.5/PM10
- 0.78
- Wind
- light
- Recent rain
- 0h in last 6h
- Pattern
- stagnant smoke
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
- 3:55 AM
- Moonset
- 12:51 PM
- In sign
- ♑︎ Capricorn
Fireflies rise from the lawn
Princeton at a glance
- Today vs. normal: 6°F above the seasonal normal for this latitude
- Last frost: April 24 (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 — Princeton
SPC has placed Princeton in the Marginal Risk category for severe thunderstorms day after tomorrow.
- TODAYNONENo severe risk
- TOMORROWNONENo severe risk
- DAY 3MRGLMarginal Risk
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.