Harristown, IL Weather & Growing Conditions
Today
90°F
Slight Chance Showers And Thunderstorms
A slight chance of showers and thunderstorms between 11am and 1pm. Mostly cloudy, with a high near 90. South southwest wind around 8 mph. Chance of precipitation is 20%.
7-day forecast
| When | Temp | Forecast | Wind | Precip |
|---|---|---|---|---|
| Today | 90°F | Slight Chance Showers And Thunderstorms | 8 mph SSW | 15% |
| Tonight | 69°F | Partly Cloudy then Slight Chance Showers And Thunderstorms | 6 mph SSW | 20% |
| Sunday | 82°F | Chance Showers And Thunderstorms | 3 to 12 mph N | 48% |
| Sunday Night | 60°F | Chance Showers And Thunderstorms | 15 mph NE | 62% |
| Monday | 70°F | Showers And Thunderstorms Likely | 16 mph NE | 70% |
| Monday Night | 54°F | Chance Rain Showers | 15 mph NE | 49% |
| Tuesday | 67°F | Slight Chance Rain Showers | 16 mph NE | 20% |
| Tuesday Night | 52°F | Slight Chance Rain Showers then Mostly Cloudy | 8 to 15 mph NNE | 17% |
| Wednesday | 70°F | Mostly Sunny | 13 mph NNE | 3% |
| Wednesday Night | 53°F | Partly Cloudy | 5 to 12 mph NNE | 2% |
| Thursday | 72°F | Mostly Sunny | 7 to 10 mph NNE | 2% |
| Thursday Night | 55°F | Partly Cloudy | 5 to 9 mph NNE | 2% |
| Friday | 74°F | Mostly Sunny | 6 to 10 mph NE | 2% |
| Friday Night | 54°F | Partly Cloudy | 5 to 9 mph NE | 2% |
Forecast source: National Weather Service (api.weather.gov). Updated through the day.
Growing snapshot for Harristown, IL
Last spring frost
Apr 14
First fall frost
Oct 24
Growing season
192 days
Hardiness zone
6a
Explore more for Harristown, IL: full frost dates · planting calendar · Illinois frost dates
Climate data from the nearest NOAA station, Decatur Wtp, Il (7.7 mi). Frost dates are 1991–2020 averages, not a forecast. Page updated Sep 19, 2026.