Winthrop Harbor, IL Weather & Growing Conditions
Tonight
60°F
Showers And Thunderstorms Likely
A slight chance of rain showers before 11pm, then showers and thunderstorms likely between 11pm and 5am, then showers and thunderstorms. Some of the storms could produce heavy rain. Cloudy, with a low around 60. East southeast wind 15 to 20 mph. Chance of precipitation is 80%. New rainfall amounts between three quarters and one inch possible.
7-day forecast
| When | Temp | Forecast | Wind | Precip |
|---|---|---|---|---|
| Tonight | 60°F | Showers And Thunderstorms Likely | 15 to 20 mph ESE | 82% |
| Saturday | 74°F | Showers And Thunderstorms then Showers And Thunderstorms Likely | 15 to 20 mph SE | 97% |
| Saturday Night | 62°F | Showers And Thunderstorms Likely then Showers And Thunderstorms | 10 to 15 mph NE | 77% |
| Sunday | 67°F | Showers And Thunderstorms Likely | 15 to 25 mph NNE | 67% |
| Sunday Night | 54°F | Chance Rain Showers | 20 mph NE | 39% |
| Monday | 65°F | Chance Rain Showers | 20 to 25 mph ENE | 34% |
| Monday Night | 52°F | Chance Rain Showers | 10 to 20 mph ENE | 32% |
| Tuesday | 64°F | Slight Chance Rain Showers | 15 mph NE | 20% |
| Tuesday Night | 52°F | Slight Chance Rain Showers then Mostly Cloudy | 10 to 15 mph ENE | 18% |
| Wednesday | 65°F | Partly Sunny | 10 mph NE | 13% |
| Wednesday Night | 52°F | Mostly Cloudy | 5 to 10 mph NNE | 5% |
| Thursday | 66°F | Partly Sunny | 5 to 10 mph NNE | 5% |
| Thursday Night | 53°F | Mostly Cloudy | 5 mph NNE | 5% |
| Friday | 68°F | Mostly Sunny | 5 to 10 mph NNE | 5% |
Forecast source: National Weather Service (api.weather.gov). Updated through the day.
Growing snapshot for Winthrop Harbor, IL
Last spring frost
Apr 30
First fall frost
Oct 21
Growing season
173 days
Hardiness zone
6a
Explore more for Winthrop Harbor, IL: full frost dates · planting calendar · Illinois frost dates
Climate data from the nearest NOAA station, Chicago Waukegan Rgnl Ap, Il (4.8 mi). Frost dates are 1991–2020 averages, not a forecast. Page updated Sep 19, 2026.