Cortland, IL Weather & Growing Conditions
Tonight
62°F
Slight Chance Rain Showers then Chance Showers And Thunderstorms
A slight chance of rain showers before 7pm, then a chance of showers and thunderstorms. Mostly cloudy, with a low around 62. East southeast wind 10 to 15 mph. Chance of precipitation is 50%. New rainfall amounts between a half and three quarters of an inch possible.
7-day forecast
| When | Temp | Forecast | Wind | Precip |
|---|---|---|---|---|
| Tonight | 62°F | Slight Chance Rain Showers then Chance Showers And Thunderstorms | 10 to 15 mph ESE | 50% |
| Saturday | 77°F | Showers And Thunderstorms Likely | 5 to 15 mph SE | 86% |
| Saturday Night | 63°F | Showers And Thunderstorms Likely then Showers And Thunderstorms | 5 to 10 mph NE | 80% |
| Sunday | 68°F | Showers And Thunderstorms | 10 to 20 mph NNE | 78% |
| Sunday Night | 55°F | Rain Showers Likely | 15 mph NE | 61% |
| Monday | 64°F | Chance Rain Showers | 15 mph ENE | 49% |
| Monday Night | 50°F | Chance Rain Showers | 10 to 15 mph ENE | 33% |
| Tuesday | 63°F | Chance Rain Showers | 10 to 15 mph NE | 27% |
| Tuesday Night | 49°F | Mostly Cloudy | 5 to 15 mph NE | 11% |
| Wednesday | 66°F | Partly Sunny | 10 to 15 mph NNE | 6% |
| Wednesday Night | 50°F | Partly Cloudy | 5 to 10 mph NNE | 4% |
| Thursday | 69°F | Partly Sunny | 5 to 10 mph NNE | 4% |
| Thursday Night | 52°F | Partly Cloudy | 5 mph NNE | 4% |
| Friday | 70°F | Mostly Sunny | 5 to 10 mph NNE | 5% |
Forecast source: National Weather Service (api.weather.gov). Updated through the day.
Growing snapshot for Cortland, IL
Last spring frost
Apr 24
First fall frost
Oct 18
Growing season
177 days
Hardiness zone
5b
Explore more for Cortland, IL: full frost dates · planting calendar · Illinois frost dates
Climate data from the nearest NOAA station, De Kalb, Il (4.4 mi). Frost dates are 1991–2020 averages, not a forecast. Page updated Sep 19, 2026.