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Will it freeze in Helena in the next 7 nights?
The earliest overnight low at or below 32°F in the available NWS frost forecast is Tonight: 27°F (Thu, Nov 5, 6:00 PM MST to Fri, Nov 6, 6:00 AM MST).
Tonight: forecast low 27°F. Hard freeze.
NWS forecast period: Thu, Nov 5, 6:00 PM MST to Fri, Nov 6, 6:00 AM MST.
7 of the next 7 nights are forecast at 36°F or colder, cold enough for frost on exposed plants.
- Tonight 27°F Hard freeze · Mostly Clear
- Fri, Nov 6 34°F Frost possible · Partly Cloudy
- Sat, Nov 7 34°F Frost possible · Partly Cloudy
- Sun, Nov 8 32°F Freeze · Mostly Cloudy
- Mon, Nov 9 33°F Frost possible · Mostly Cloudy
- Tue, Nov 10 36°F Frost possible · Partly Cloudy
- 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 Helena
The median first fall hard-freeze date (28°F) is October 7, from NOAA’s 1991–2020 Climate Normals at Helena 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 | May 10 · May 25 · Jun 13 | Sep 4 · Sep 19 · Oct 1 | 114 days |
| 32°F freeze | Apr 29 · May 9 · May 25 | Sep 17 · Sep 30 · Oct 11 | 142 days |
| 28°F hard freeze | Apr 15 · Apr 29 · May 11 | Sep 25 · Oct 7 · Oct 22 | 162 days |
Average high temperature by month
1991–2020 normals at Helena 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 Helena, MT come from the nearest weather station with freeze statistics in NOAA’s 1991–2020 Climate Normals: Helena Regional Airport (station USW00024144, elevation 3,828 ft), 2.7 mi from Helena. 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 Helena
| City | Distance | Last spring frost | First fall frost |
|---|---|---|---|
| Butte, MT | 57 mi | Jun 13 | Sep 5 |
| Anaconda, MT | 64 mi | Jun 1 | Sep 14 |
| Belgrade, MT | 69 mi | May 26 | Sep 16 |
| Great Falls, MT | 71 mi | May 6 | Oct 1 |
| Bozeman, MT | 78 mi | May 26 | Sep 22 |
| Livingston, MT | 95 mi | May 27 | Sep 14 |
| Missoula, MT | 97 mi | May 10 | Oct 1 |
| Hamilton, MT | 104 mi | May 21 | Sep 22 |
| Polson, MT | 125 mi | May 10 | Oct 5 |
| Lewistown, MT | 126 mi | May 23 | Sep 21 |
Frequently asked questions
When is the last frost in Helena?
On average, the last spring frost (32°F) in Helena is around May 9. In about 1 year in 10 it comes after May 25, and in 9 years in 10 it comes after April 29.
When is the first frost in Helena?
The first fall frost (32°F) usually arrives around September 30. There’s a 10% chance of a freeze by September 17 and a 90% chance by October 11.
Can it frost in Helena 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 25.
What growing zone is Helena?
Helena is in USDA Plant Hardiness Zone 5a (average annual extreme minimum temperature −20 to −15°F), based on the 2023 USDA map for ZIP code 59623. See growing zones in Montana.
More: all Montana frost dates · Montana growing zones · UV index today in Helena · frost vs. freeze