Seneca, IL Weather & Growing Conditions
Overnight
63°F
Mostly Clear
Mostly clear. Low around 63, with temperatures rising to around 65 overnight. South wind around 5 mph.
7-day forecast
| When | Temp | Forecast | Wind | Precip |
|---|---|---|---|---|
| Overnight | 63°F | Mostly Clear | 5 mph S | 0% |
| Tuesday | 85°F | Mostly Sunny | 5 mph SSW | 5% |
| Tuesday Night | 68°F | Mostly Cloudy | 5 mph SSW | 11% |
| Wednesday | 82°F | Chance Showers And Thunderstorms | 0 to 5 mph WSW | 56% |
| Wednesday Night | 67°F | Showers And Thunderstorms | 0 to 5 mph WNW | 90% |
| Thursday | 81°F | Chance Showers And Thunderstorms | 0 to 5 mph SE | 73% |
| Thursday Night | 64°F | Chance Showers And Thunderstorms then Partly Cloudy | 0 to 5 mph SSE | 29% |
| Friday | 84°F | Mostly Sunny | 0 to 5 mph S | 6% |
| Friday Night | 66°F | Partly Cloudy | 0 mph | 8% |
| Saturday | 86°F | Mostly Sunny | 0 to 5 mph SSW | 11% |
| Saturday Night | 71°F | Mostly Clear | 5 mph SSW | 11% |
| Sunday | 88°F | Mostly Sunny | 5 to 10 mph SW | 10% |
| Sunday Night | 72°F | Slight Chance Showers And Thunderstorms | 5 to 10 mph SSW | 30% |
| Monday | 88°F | Chance Showers And Thunderstorms | 5 to 10 mph SSW | 30% |
Forecast source: National Weather Service (api.weather.gov). Updated through the day.
Growing snapshot for Seneca, IL
Last spring frost
Apr 27
First fall frost
Oct 17
Growing season
171 days
Hardiness zone
5b
Explore more for Seneca, IL: full frost dates · planting calendar · Illinois frost dates
Climate data from the nearest NOAA station, Marseilles Lock, Il (7.9 mi). Frost dates are 1991–2020 averages, not a forecast. Page updated Aug 4, 2026.