Ottawa, IL Weather & Growing Conditions
Today
85°F
Mostly Sunny
Mostly sunny, with a high near 85. South southwest wind around 5 mph, with gusts as high as 15 mph.
7-day forecast
| When | Temp | Forecast | Wind | Precip |
|---|---|---|---|---|
| Today | 85°F | Mostly Sunny | 5 mph SSW | 0% |
| Tonight | 68°F | Mostly Cloudy then Slight Chance Showers And Thunderstorms | 5 mph S | 19% |
| Wednesday | 80°F | Showers And Thunderstorms Likely then Chance Showers And Thunderstorms | 5 mph WSW | 59% |
| Wednesday Night | 66°F | Showers And Thunderstorms | 0 to 5 mph NNW | 88% |
| Thursday | 80°F | Chance Showers And Thunderstorms | 5 mph ESE | 66% |
| Thursday Night | 63°F | Slight Chance Showers And Thunderstorms then Partly Cloudy | 0 to 5 mph SE | 24% |
| Friday | 82°F | Mostly Sunny | 0 to 5 mph SSE | 6% |
| Friday Night | 65°F | Mostly Clear | 0 to 5 mph S | 9% |
| Saturday | 85°F | Mostly Sunny | 5 mph SSW | 9% |
| Saturday Night | 70°F | Mostly Clear | 5 to 10 mph SSW | 12% |
| Sunday | 87°F | Mostly Sunny | 10 to 15 mph SW | 12% |
| Sunday Night | 70°F | Slight Chance Showers And Thunderstorms | 5 to 10 mph SSW | 29% |
| Monday | 86°F | Chance Showers And Thunderstorms | 5 to 10 mph SSW | 29% |
| Monday Night | 71°F | Chance Showers And Thunderstorms | 10 mph WSW | 37% |
Forecast source: National Weather Service (api.weather.gov). Updated through the day.
Growing snapshot for Ottawa, IL
Last spring frost
Apr 20
First fall frost
Oct 22
Growing season
183 days
Hardiness zone
5b
Explore more for Ottawa, IL: full frost dates · planting calendar · Illinois frost dates
Climate data from the nearest NOAA station, Ottawa 5Sw, Il (3.8 mi). Frost dates are 1991–2020 averages, not a forecast. Page updated Aug 4, 2026.