Seneca, IL Weather & Growing Conditions
This Afternoon
81°F
Chance Showers And Thunderstorms
A chance of showers and thunderstorms before 3pm, then a slight chance of showers and thunderstorms. Cloudy, with a high near 81. Southeast wind around 5 mph, with gusts as high as 15 mph. Chance of precipitation is 30%. New rainfall amounts between a tenth and quarter of an inch possible.
7-day forecast
| When | Temp | Forecast | Wind | Precip |
|---|---|---|---|---|
| This Afternoon | 81°F | Chance Showers And Thunderstorms | 5 mph SE | 28% |
| Tonight | 67°F | Showers And Thunderstorms | 5 mph SW | 90% |
| Sunday | 73°F | Showers And Thunderstorms Likely | 5 to 15 mph N | 66% |
| Sunday Night | 58°F | Chance Showers And Thunderstorms | 15 mph NE | 46% |
| Monday | 66°F | Rain Showers Likely | 15 mph ENE | 56% |
| Monday Night | 53°F | Chance Rain Showers | 10 to 15 mph NE | 42% |
| Tuesday | 65°F | Slight Chance Rain Showers | 10 to 15 mph NE | 20% |
| Tuesday Night | 53°F | Mostly Cloudy | 5 to 15 mph NNE | 12% |
| Wednesday | 68°F | Mostly Sunny | 5 to 10 mph NNE | 7% |
| Wednesday Night | 54°F | Partly Cloudy | 5 to 10 mph NNE | 1% |
| Thursday | 70°F | Partly Sunny | 5 mph NNE | 3% |
| Thursday Night | 54°F | Mostly Cloudy | 0 to 5 mph NE | 3% |
| Friday | 74°F | Mostly Sunny | 0 to 5 mph NE | 3% |
| Friday Night | 54°F | Partly Cloudy | 0 to 5 mph NE | 2% |
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 Sep 19, 2026.