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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.

Today
77°F
Showers And Thunderstorms then Showers And Thunderstorms Likely
Showers and thunderstorms before noon, then showers and thunderstorms likely between noon and 5pm, then showers and thunderstorms likely. Cloudy. High near 77, with temperatures falling to around 75 in the afternoon. Southeast wind around 10 mph. Chance of precipitation is 100%. New rainfall amounts between three quarters and one inch possible.

7-day forecast for Cortland

WhenTempForecastWindPrecip
Today 77°F Showers And Thunderstorms then Showers And Thunderstorms Likely 10 mph SE 100%
Tonight 62°F Showers And Thunderstorms 5 to 10 mph ESE 95%
Sunday 69°F Showers And Thunderstorms Likely 10 to 15 mph NNE 58%
Sunday Night 54°F Chance Rain Showers 10 to 15 mph NE 30%
Monday 63°F Chance Rain Showers 15 mph ENE 44%
Monday Night 50°F Slight Chance Rain Showers then Mostly Cloudy 10 to 15 mph NE 19%
Tuesday 62°F Slight Chance Rain Showers 10 to 15 mph NE 17%
Tuesday Night 48°F Partly Cloudy 10 to 15 mph NE 12%
Wednesday 65°F Mostly Sunny 10 to 15 mph NE 5%
Wednesday Night 50°F Partly Cloudy 5 to 10 mph NNE 1%
Thursday 67°F Partly Sunny 5 to 10 mph NNE 4%
Thursday Night 50°F Partly Cloudy 5 to 10 mph NE 3%
Friday 71°F Mostly Sunny 5 to 10 mph NE 3%
Friday Night 50°F Partly Cloudy 5 mph NE 3%

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.