Harrisburg, IL Weather & Growing Conditions
Local forecast, frost dates, hardiness zone and planting guidance for Harrisburg, a city in Saline County, Illinois.
This Afternoon
100°F
Slight Chance Showers And Thunderstorms
A slight chance of rain showers between 3pm and 4pm, then a slight chance of showers and thunderstorms. Sunny. High near 100, with temperatures falling to around 97 in the afternoon. Heat index values as high as 106. West southwest wind around 7 mph. Chance of precipitation is 20%.
7-day forecast for Harrisburg
| When | Temp | Forecast | Wind | Precip |
|---|---|---|---|---|
| This Afternoon | 100°F | Slight Chance Showers And Thunderstorms | 7 mph WSW | 20% |
| Tonight | 71°F | Slight Chance Showers And Thunderstorms then Partly Cloudy | 0 to 3 mph ESE | 23% |
| Saturday | 99°F | Sunny | 1 to 7 mph SW | 5% |
| Saturday Night | 73°F | Partly Cloudy | 3 mph SSW | 2% |
| Sunday | 98°F | Sunny | 3 to 7 mph WSW | 7% |
| Sunday Night | 70°F | Partly Cloudy | 3 mph N | 9% |
| Monday | 89°F | Partly Sunny then Chance Showers And Thunderstorms | 1 to 9 mph N | 39% |
| Monday Night | 62°F | Chance Showers And Thunderstorms | 5 to 9 mph NNE | 40% |
| Tuesday | 77°F | Chance Showers And Thunderstorms | 6 to 12 mph N | 26% |
| Tuesday Night | 57°F | Mostly Cloudy | 5 to 12 mph N | 8% |
| Wednesday | 77°F | Mostly Sunny | 5 to 9 mph N | 3% |
| Wednesday Night | 56°F | Partly Cloudy | 2 to 8 mph NNE | 3% |
| Thursday | 78°F | Mostly Sunny | 2 to 8 mph N | 3% |
| Thursday Night | 58°F | Partly Cloudy | 2 to 7 mph NNE | 3% |
Forecast source: National Weather Service (api.weather.gov) for Harrisburg (37.738, -88.546). Updated through the day.
Growing snapshot for Harrisburg
Last spring frost
Apr 7
First fall frost
Oct 26
Growing season
202 days
Hardiness zone
7a
More local growing data for Harrisburg: nearby ZIP 62965 weather · frost dates · planting calendar · Illinois frost dates
Nearby towns & communities
Climate data from the nearest NOAA station, Harrisburg, Il (1.9 mi from Harrisburg). Frost dates are 1991–2020 averages, not a forecast. Page updated Sep 18, 2026.