Cortland, IL Weather & Growing Conditions
Local forecast, frost dates, hardiness zone and planting guidance for Cortland, a town in Dekalb County, Illinois.
Tonight
56°F
Rain Showers
Rain showers. Cloudy. Low around 56, with temperatures rising to around 60 overnight. South wind around 15 mph, with gusts as high as 30 mph. Chance of precipitation is 90%. New rainfall amounts between a quarter and half of an inch possible.
7-day forecast for Cortland
| When | Temp | Forecast | Wind | Precip |
|---|---|---|---|---|
| Tonight | 56°F | Rain Showers | 15 mph S | 90% |
| Wednesday | 60°F | Chance Rain Showers | 15 mph SSW | 50% |
| Wednesday Night | 46°F | Slight Chance Rain Showers | 15 mph SW | 19% |
| Thursday | 54°F | Chance Rain Showers | 10 to 15 mph WSW | 37% |
| Thursday Night | 41°F | Chance Rain Showers | 5 to 10 mph NW | 39% |
| Friday | 50°F | Slight Chance Rain Showers then Mostly Cloudy | 10 to 15 mph N | 20% |
| Friday Night | 33°F | Partly Cloudy | 5 to 10 mph NNW | 3% |
| Saturday | 51°F | Mostly Sunny | 0 to 5 mph WNW | 3% |
| Saturday Night | 33°F | Partly Cloudy | 0 to 5 mph WSW | 4% |
| Sunday | 56°F | Mostly Sunny | 5 to 10 mph W | 14% |
| Sunday Night | 34°F | Mostly Clear | 5 mph W | 5% |
| Monday | 60°F | Sunny | 5 to 15 mph WSW | 3% |
| Monday Night | 39°F | Mostly Clear | 5 to 10 mph W | 1% |
| Tuesday | 61°F | Sunny | 5 to 10 mph WNW | 1% |
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 Nov 4, 2026.