St. Johns, Illinois Weather
Cicadas claim the scorching afternoon. Day 15 of summer. Read this microseason across nine climate regions →
St. Johns weather forecast — hour by hour, 7-day outlook, NOAA radar
- TodayJul 5Overcast13%—87°70°—
- MondayJul 6Overcast13%—89°71°+2°
- TuesdayJul 7Light Drizzle13%—84°69°-5°
- WednesdayJul 8Partly Cloudy——87°64°+3°
- ThursdayJul 9Overcast34%—92°73°+5°
- FridayJul 10Light Showers45%0.19″91°70°-1°
- SaturdayJul 11Drizzle41%—85°70°-6°
AQI 40 (Good), driven by PM2.5. AQI flat over the last 6 hours (within ±3 points). PM2.5 at 9.5 µg/m³ (AQI 52) with a 0.83 fine-to-coarse ratio and 1 mph wind — combustion smoke trapped in calm air, not road dust.
OK No precautions needed for the general population; unusually sensitive individuals may consider limiting prolonged outdoor exertion during the projected peak around 10 PM.
What's driving it
Ozone × UV × Sky
Ozone at AQI 43. Overcast through the UV peak window (cloud cover ~100%) — afternoon ozone should stay flat.
- Present
- AQI 43
- UV peak
- 5.4 at 1 PM
- Sky at peak
- overcast
- Projected peak
- AQI 15
PM × Wind × Precip
PM2.5 at 9.5 µg/m³ (AQI 52) with a 0.83 fine-to-coarse ratio and 1 mph wind — combustion smoke trapped in calm air, not road dust.
- PM2.5/PM10
- 0.83
- Wind
- calm
- 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).
If the first of July be rainy weather, 'twill rain more or less for four weeks together.
- Moonrise
- 11:13 PM
- Moonset
- 11:09 AM
- In sign
- ♓︎ Pisces
Cicadas claim the scorching afternoon
St. Johns at a glance
- Today vs. normal: 7°F above the seasonal normal for this latitude
- Last frost: April 4 (climatological average for this latitude)
- Microseason: Jul 1–5
- Planting window: Harvest early potatoes. Begin drying onions on the surface.
16-Day Forecast — St. Johns
- Sun86°70°13%
- Mon89°71°13%
- Tue84°69°13%
- Wed87°64°7%
- Thu92°73°34%
- Fri91°70°45%
- Sat85°70°41%
- Sun91°70°21%
- Mon92°73°12%
- Tue100°76°7%
- Wed84°70°9%
- Thu84°61°16%
- Fri91°64°28%
- Sat95°68°30%
- Sun95°73°32%
- Mon94°77°26%
Forecast data from Open-Meteo (CC BY 4.0).
Right now in the garden
Peak growing season
As of July 5, 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 — St. Johns
SPC includes St. Johns in the general thunderstorm area today — no severe risk, but storms are possible.
- TODAYTSTMGeneral Thunderstorms
- TOMORROWTSTMGeneral Thunderstorms
- DAY 3NONENo severe risk
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.
ZIP codes in St. Johns
- 62832