Ottawa, IL Weather & Growing Conditions
Tonight
66°F
Mostly Cloudy then Chance Showers And Thunderstorms
A chance of showers and thunderstorms after 2am. Mostly cloudy, with a low around 66. East southeast wind around 10 mph, with gusts as high as 20 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 |
|---|---|---|---|---|
| Tonight | 66°F | Mostly Cloudy then Chance Showers And Thunderstorms | 10 mph ESE | 28% |
| Saturday | 82°F | Showers And Thunderstorms Likely | 5 to 10 mph SE | 63% |
| Saturday Night | 66°F | Showers And Thunderstorms Likely | 5 mph NNE | 79% |
| Sunday | 71°F | Showers And Thunderstorms | 10 to 15 mph NE | 79% |
| Sunday Night | 58°F | Showers And Thunderstorms Likely | 15 mph NE | 71% |
| Monday | 66°F | Showers And Thunderstorms Likely | 15 mph ENE | 61% |
| Monday Night | 54°F | Chance Rain Showers | 10 to 15 mph NE | 34% |
| Tuesday | 65°F | Chance Rain Showers | 10 to 15 mph NE | 27% |
| Tuesday Night | 52°F | Mostly Cloudy | 5 to 10 mph NNE | 8% |
| Wednesday | 68°F | Partly Sunny | 5 to 10 mph NNE | 5% |
| Wednesday Night | 52°F | Partly Cloudy | 5 to 10 mph NNE | 5% |
| Thursday | 69°F | Mostly Sunny | 5 mph NNE | 2% |
| Thursday Night | 55°F | Partly Cloudy | 0 to 5 mph NNE | 4% |
| Friday | 72°F | Mostly Sunny | 5 mph NNE | 4% |
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 Sep 19, 2026.