Cortland, IL Weather & Growing Conditions
Local forecast, frost dates, hardiness zone and planting guidance for Cortland, a town in Dekalb County, Illinois.
Today
83°F
Mostly Sunny
Mostly sunny, with a high near 83. South southwest wind 5 to 10 mph.
7-day forecast for Cortland
| When | Temp | Forecast | Wind | Precip |
|---|---|---|---|---|
| Today | 83°F | Mostly Sunny | 5 to 10 mph SSW | 1% |
| Tonight | 66°F | Mostly Cloudy then Slight Chance Showers And Thunderstorms | 5 mph WSW | 51% |
| Wednesday | 77°F | Showers And Thunderstorms Likely | 5 mph WSW | 74% |
| Wednesday Night | 62°F | Showers And Thunderstorms | 5 mph NW | 83% |
| Thursday | 77°F | Rain Showers Likely then Slight Chance Showers And Thunderstorms | 0 to 5 mph ENE | 56% |
| Thursday Night | 60°F | Slight Chance Showers And Thunderstorms then Partly Cloudy | 0 to 5 mph SE | 20% |
| Friday | 80°F | Mostly Sunny | 0 to 5 mph SSE | 7% |
| Friday Night | 62°F | Mostly Clear | 0 to 5 mph SSW | 9% |
| Saturday | 82°F | Mostly Sunny | 5 to 10 mph SSW | 10% |
| Saturday Night | 67°F | Partly Cloudy then Slight Chance Showers And Thunderstorms | 5 to 10 mph SSW | 18% |
| Sunday | 84°F | Slight Chance Showers And Thunderstorms | 10 to 15 mph SW | 18% |
| Sunday Night | 68°F | Chance Showers And Thunderstorms | 5 to 10 mph SSW | 40% |
| Monday | 83°F | Chance Rain Showers | 5 to 10 mph SSW | 38% |
| Monday Night | 68°F | Chance Showers And Thunderstorms | 10 mph W | 44% |
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
Nearby towns & communities
DeKalb
Genoa
Hinckley
Kingston
Kirkland
Lake Holiday
Malta
Sandwich
Shabbona
Somonauk
Sycamore
Waterman
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 Aug 4, 2026.