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Will it freeze in Union Grove in the next 7 nights?
The earliest overnight low at or below 32°F in the available NWS frost forecast is Fri, Nov 6: 29°F (Fri, Nov 6, 6:00 PM CST to Sat, Nov 7, 6:00 AM CST).
Tonight: forecast low 36°F. Frost possible.
NWS forecast period: Thu, Nov 5, 6:00 PM CST to Fri, Nov 6, 6:00 AM CST.
5 of the next 7 nights are forecast at 36°F or colder, cold enough for frost on exposed plants.
- Tonight 36°F Frost possible · Isolated Rain Showers then Mostly Cloudy
- Fri, Nov 6 29°F Freeze · Mostly Clear
- Sat, Nov 7 32°F Freeze · Partly Cloudy
- Sun, Nov 8 34°F Frost possible · Mostly Clear
- Mon, Nov 9 39°F Above 36°F · Mostly Clear
- Tue, Nov 10 36°F Frost possible · Partly Cloudy
- Wed, Nov 11 37°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 Union Grove
The median first fall hard-freeze date (28°F) is October 20, from NOAA’s 1991–2020 Climate Normals at Union Grove. 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 | May 1 · May 17 · May 31 | Sep 18 · Sep 30 · Oct 12 | 136 days |
| 32°F freeze | Apr 21 · May 5 · May 20 | Sep 27 · Oct 8 · Oct 23 | 156 days |
| 28°F hard freeze | Apr 9 · Apr 23 · May 10 | Oct 4 · Oct 20 · Nov 3 | 178 days |
Average high temperature by month
1991–2020 normals at Union Grove
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 Union Grove, WI come from the nearest weather station with freeze statistics in NOAA’s 1991–2020 Climate Normals: Union Grove (station USC00478723, elevation 730 ft), 0.9 mi from Union Grove. 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 Union Grove
| City | Distance | Last spring frost | First fall frost |
|---|---|---|---|
| Sturtevant, WI | 7.5 mi | Apr 20 | Oct 24 |
| Mount Pleasant, WI | 8.7 mi | Apr 20 | Oct 24 |
| Somers, WI | 8.7 mi | Apr 28 | Oct 19 |
| Waterford, WI | 9.9 mi | May 5 | Oct 10 |
| Bristol, WI | 11 mi | Apr 30 | Oct 15 |
| Kenosha, WI | 11 mi | Apr 28 | Oct 19 |
| Salem Lakes, WI | 11 mi | Apr 30 | Oct 15 |
| Burlington, WI | 11 mi | May 5 | Oct 9 |
| Caledonia, WI | 12 mi | Apr 24 | Oct 24 |
| Racine, WI | 12 mi | Apr 20 | Oct 24 |
Frequently asked questions
When is the last frost in Union Grove?
On average, the last spring frost (32°F) in Union Grove is around May 5. In about 1 year in 10 it comes after May 20, and in 9 years in 10 it comes after April 21.
When is the first frost in Union Grove?
The first fall frost (32°F) usually arrives around October 8. There’s a 10% chance of a freeze by September 27 and a 90% chance by October 23.
Can it frost in Union Grove 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 17.
What growing zone is Union Grove?
Union Grove is in USDA Plant Hardiness Zone 5b (average annual extreme minimum temperature −15 to −10°F), based on the 2023 USDA map for ZIP code 53182. See growing zones in Wisconsin.
More: all Wisconsin frost dates · Wisconsin growing zones · frost vs. freeze