Checking current alerts… View NWS forecast and alerts.
Will it freeze in Winthrop Harbor in the next 7 nights?
No overnight lows at or below 32°F are forecast in Winthrop Harbor during the next 7 nights in the available NWS frost forecast.
Tonight: forecast low 37°F. Above 36°F.
NWS forecast period: Thu, Nov 5, 6:00 PM CST to Fri, Nov 6, 6:00 AM CST.
2 of the next 7 nights are forecast at 36°F or colder, cold enough for frost on exposed plants.
- Tonight 37°F Above 36°F · Chance Rain Showers then Mostly Cloudy
- Fri, Nov 6 33°F Frost possible · Partly Cloudy
- Sat, Nov 7 35°F Frost possible · Partly Cloudy
- Sun, Nov 8 37°F Above 36°F · Mostly Clear
- Mon, Nov 9 41°F Above 36°F · Mostly Clear
- Tue, Nov 10 39°F Above 36°F · Partly Cloudy
- Wed, Nov 11 40°F Above 36°F · Partly Cloudy
Overnight lows from the National Weather Service forecast for this location. This covers the available forecast window, not the first freeze of the whole season. Frost can form above 32°F on clear, calm nights.
Frost and freeze probabilities
Freeze dates shift from year to year. Spring percentages describe the chance of a freeze after the stated date; fall percentages describe the chance of a freeze by that date. The 10% spring date is the cautious one: a later freeze happens about 1 year in 10.
These dates describe historical probabilities, not this year’s forecast or the earliest and latest possible freezes. Different weather stations or probability thresholds can produce different published dates for the same city.
Average first hard freeze in Winthrop Harbor
The median first fall hard-freeze date (28°F) is November 1, from NOAA’s 1991–2020 Climate Normals at Chicago Waukegan Regional Airport. This is the 50% probability date, not a forecast for this year.
| Temperature | Last spring date 90% · 50% · 10% chance of a later freeze | First fall date 10% · 50% · 90% chance of an earlier freeze | Season |
|---|---|---|---|
| 36°F frost possible | Apr 28 · May 12 · May 27 | Sep 25 · Oct 10 · Oct 22 | 150 days |
| 32°F freeze | Apr 14 · Apr 30 · May 16 | Oct 5 · Oct 21 · Nov 2 | 173 days |
| 28°F hard freeze | Apr 2 · Apr 16 · May 2 | Oct 15 · Nov 1 · Nov 14 | 197 days |
Average high temperature by month
1991–2020 normals at Chicago Waukegan Regional Airport
Average low temperature by month
Months with lows near or below freezing carry frost risk
Where these frost dates come from
The frost dates for Winthrop Harbor, IL come from the nearest weather station with freeze statistics in NOAA’s 1991–2020 Climate Normals: Chicago Waukegan Regional Airport (station USW00014880, elevation 727 ft), 4.8 mi from Winthrop Harbor. Local conditions (valleys, hilltops, distance to water, city heat) can shift frost dates by days or weeks. The hardiness zone is from the 2023 USDA Plant Hardiness Zone Map (USDA ARS and Oregon State University PRISM). See our methodology.
Frost dates near Winthrop Harbor
| City | Distance | Last spring frost | First fall frost |
|---|---|---|---|
| Zion, IL | 1.9 mi | Apr 30 | Oct 21 |
| Beach Park, IL | 3.7 mi | Apr 30 | Oct 21 |
| Pleasant Prairie, WI | 4.3 mi | Apr 19 | Oct 26 |
| Kenosha, WI | 8.1 mi | Apr 28 | Oct 19 |
| Waukegan, IL | 8.1 mi | Apr 30 | Oct 19 |
| Park City, IL | 9.3 mi | Apr 30 | Oct 19 |
| Gurnee, IL | 9.3 mi | Apr 30 | Oct 19 |
| Bristol, WI | 9.9 mi | Apr 30 | Oct 15 |
| Lindenhurst, IL | 11 mi | Apr 24 | Oct 23 |
| North Chicago, IL | 11 mi | Apr 30 | Oct 19 |
Frequently asked questions
When is the last frost in Winthrop Harbor?
On average, the last spring frost (32°F) in Winthrop Harbor is around April 30. In about 1 year in 10 it comes after May 16, and in 9 years in 10 it comes after April 14.
When is the first frost in Winthrop Harbor?
The first fall frost (32°F) usually arrives around October 21. There’s a 10% chance of a freeze by October 5 and a 90% chance by November 2.
Can it frost in Winthrop Harbor after the last frost date?
Yes. Frost can form on clear, calm nights even when the air stays above 32°F. Temperatures of 36°F or lower, cold enough for frost on exposed plants, have a 50% chance of occurring after May 12.
What growing zone is Winthrop Harbor?
Winthrop Harbor is in USDA Plant Hardiness Zone 6a (average annual extreme minimum temperature −10 to −5°F), based on the 2023 USDA map for ZIP code 60096. See growing zones in Illinois.
More: all Illinois frost dates · Illinois growing zones · frost vs. freeze