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
| When | Temp | Forecast | Wind | Precip |
|---|---|---|---|---|
| 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
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 Sep 19, 2026.