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Will it freeze in Union in the next 7 nights?
No overnight lows at or below 32°F are forecast in Union during the next 7 nights in the available NWS frost forecast.
Tonight: forecast low 45°F. Above 36°F.
NWS forecast period: Thu, Nov 5, 6:00 PM EST to Fri, Nov 6, 6:00 AM EST.
5 of the next 7 nights are forecast at 36°F or colder, cold enough for frost on exposed plants.
- Tonight 45°F Above 36°F · Mostly Cloudy
- Fri, Nov 6 36°F Frost possible · Partly Cloudy
- Sat, Nov 7 33°F Frost possible · 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 · Mostly Clear
- Wed, Nov 11 36°F Frost possible · 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
The median first fall hard-freeze date (28°F) is November 6, from NOAA’s 1991–2020 Climate Normals at Dayton Intl 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 13 · Apr 27 · May 13 | Oct 5 · Oct 18 · Oct 30 | 173 days |
| 32°F freeze | Apr 2 · Apr 16 · May 3 | Oct 16 · Oct 28 · Nov 9 | 194 days |
| 28°F hard freeze | Mar 21 · Apr 4 · Apr 19 | Oct 26 · Nov 6 · Nov 23 | 215 days |
Average high temperature by month
1991–2020 normals at Dayton Intl 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 Union, OH come from the nearest weather station with freeze statistics in NOAA’s 1991–2020 Climate Normals: Dayton Intl Airport (station USW00093815, elevation 1,000 ft), 5.1 mi from Union. 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
| City | Distance | Last spring frost | First fall frost |
|---|---|---|---|
| Clayton, OH | 2.5 mi | Apr 16 | Oct 28 |
| Englewood, OH | 2.5 mi | Apr 16 | Oct 28 |
| Vandalia, OH | 6.8 mi | Apr 16 | Oct 28 |
| Brookville, OH | 6.8 mi | Apr 16 | Oct 28 |
| Trotwood, OH | 7.5 mi | Apr 18 | Oct 25 |
| Tipp City, OH | 8.1 mi | Apr 16 | Oct 28 |
| Dayton, OH | 9.9 mi | Apr 18 | Oct 25 |
| Troy, OH | 11 mi | Apr 18 | Oct 23 |
| Huber Heights, OH | 11 mi | Apr 16 | Oct 28 |
| Riverside, OH | 13 mi | Apr 18 | Oct 25 |
Frequently asked questions
When is the last frost in Union?
On average, the last spring frost (32°F) in Union is around April 16. In about 1 year in 10 it comes after May 3, and in 9 years in 10 it comes after April 2.
When is the first frost in Union?
The first fall frost (32°F) usually arrives around October 28. There’s a 10% chance of a freeze by October 16 and a 90% chance by November 9.
Can it frost in Union 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 April 27.
What growing zone is Union?
Union 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 45322. See growing zones in Ohio.
More: all Ohio frost dates · Ohio growing zones · frost vs. freeze