Winthrop Harbor, IL Weather & Growing Conditions
Today
81°F
Mostly Sunny
Mostly sunny, with a high near 81. South wind around 10 mph.
7-day forecast
| When | Temp | Forecast | Wind | Precip |
|---|---|---|---|---|
| Today | 81°F | Mostly Sunny | 10 mph S | 0% |
| Tonight | 67°F | Mostly Cloudy then Chance Showers And Thunderstorms | 5 to 10 mph SW | 48% |
| Wednesday | 77°F | Showers And Thunderstorms Likely | 5 mph NW | 74% |
| Wednesday Night | 62°F | Showers And Thunderstorms | 5 mph NW | 76% |
| Thursday | 76°F | Chance Rain Showers | 5 mph NNE | 50% |
| Thursday Night | 62°F | Partly Cloudy | 0 to 5 mph S | 12% |
| Friday | 80°F | Mostly Sunny | 5 mph SSW | 3% |
| Friday Night | 64°F | Mostly Clear | 5 mph S | 8% |
| Saturday | 82°F | Mostly Sunny then Slight Chance Showers And Thunderstorms | 5 to 10 mph SSW | 15% |
| Saturday Night | 68°F | Slight Chance Showers And Thunderstorms | 5 mph SW | 23% |
| Sunday | 83°F | Slight Chance Showers And Thunderstorms | 5 to 10 mph SW | 23% |
| Sunday Night | 67°F | Slight Chance Showers And Thunderstorms then Chance Showers And Thunderstorms | 5 to 10 mph WSW | 47% |
| Monday | 82°F | Chance Rain Showers | 5 to 10 mph S | 47% |
| Monday Night | 67°F | Chance Showers And Thunderstorms | 5 mph SE | 48% |
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 Aug 4, 2026.