Winthrop Harbor, IL Weather & Growing Conditions
Tonight
59°F
Rain Showers
Rain showers. Mostly cloudy, with a low around 59. South southeast wind around 15 mph, with gusts as high as 25 mph. Chance of precipitation is 80%. New rainfall amounts less than a tenth of an inch possible.
7-day forecast
| When | Temp | Forecast | Wind | Precip |
|---|---|---|---|---|
| Tonight | 59°F | Rain Showers | 15 mph SSE | 75% |
| Wednesday | 63°F | Rain Showers Likely | 15 mph SSW | 65% |
| Wednesday Night | 47°F | Mostly Cloudy then Slight Chance Rain Showers | 15 mph SW | 19% |
| Thursday | 55°F | Chance Rain Showers | 10 to 15 mph WSW | 45% |
| Thursday Night | 41°F | Rain Showers Likely | 10 to 15 mph NW | 65% |
| Friday | 51°F | Chance Rain Showers | 15 to 20 mph N | 33% |
| Friday Night | 36°F | Mostly Cloudy | 5 to 10 mph NNW | 13% |
| Saturday | 52°F | Mostly Sunny | 5 mph WNW | 7% |
| Saturday Night | 36°F | Partly Cloudy | 5 mph WSW | 7% |
| Sunday | 56°F | Mostly Sunny then Slight Chance Rain | 5 to 10 mph W | 17% |
| Sunday Night | 36°F | Partly Cloudy | 5 mph WNW | 8% |
| Monday | 58°F | Sunny | 5 to 10 mph WSW | 4% |
| Monday Night | 40°F | Partly Cloudy | 5 to 10 mph W | 3% |
| Tuesday | 58°F | Mostly Sunny | 5 to 10 mph WNW | 1% |
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 Nov 4, 2026.