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Cortland, IL Weather & Growing Conditions

Local forecast, frost dates, hardiness zone and planting guidance for Cortland, a town in Dekalb County, Illinois.

This Afternoon
71°F
Showers And Thunderstorms Likely
Showers and thunderstorms likely. Cloudy, with a high near 71. South southeast wind around 5 mph, with gusts as high as 15 mph. Chance of precipitation is 70%. New rainfall amounts between a tenth and quarter of an inch possible.

7-day forecast for Cortland

WhenTempForecastWindPrecip
This Afternoon 71°F Showers And Thunderstorms Likely 5 mph SSE 74%
Tonight 63°F Showers And Thunderstorms 5 to 10 mph SE 100%
Sunday 65°F Showers And Thunderstorms 10 to 15 mph NE 84%
Sunday Night 54°F Slight Chance Rain Showers 10 to 15 mph ENE 22%
Monday 63°F Chance Rain Showers 15 mph ENE 44%
Monday Night 50°F Chance Rain Showers 10 to 15 mph NE 44%
Tuesday 61°F Chance Rain Showers 10 to 15 mph NE 44%
Tuesday Night 49°F Mostly Cloudy 10 to 15 mph NE 11%
Wednesday 64°F Mostly Cloudy 10 to 15 mph NE 8%
Wednesday Night 50°F Mostly Cloudy 5 to 10 mph NNE 2%
Thursday 67°F Partly Sunny 5 to 10 mph NE 6%
Thursday Night 52°F Mostly Cloudy 0 to 5 mph NE 10%
Friday 71°F Partly Sunny 0 to 5 mph NE 9%
Friday Night 51°F Partly Cloudy 0 to 5 mph NE 6%

Forecast source: National Weather Service (api.weather.gov) for Cortland (41.937, -88.689). Updated through the day.

Growing snapshot for Cortland

Last spring frost
Apr 24
First fall frost
Oct 18
Growing season
177 days
Hardiness zone
5b

More local growing data for Cortland: nearby ZIP 60112 weather · frost dates · planting calendar · Illinois frost dates

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Climate data from the nearest NOAA station, De Kalb, Il (4.4 mi from Cortland). Frost dates are 1991–2020 averages, not a forecast. Page updated Sep 19, 2026.