Checking current alerts… View NWS forecast and alerts.
Will it freeze in Hamilton in the next 7 nights?
The earliest overnight low at or below 32°F in the available NWS frost forecast is Tonight: 25°F (Thu, Nov 5, 6:00 PM MST to Fri, Nov 6, 6:00 AM MST).
Tonight: forecast low 25°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 25°F Hard freeze · Partly Cloudy
- Fri, Nov 6 32°F Freeze · Mostly Cloudy
- Sat, Nov 7 34°F Frost possible · Partly Cloudy
- Sun, Nov 8 31°F Freeze · Mostly Cloudy
- Mon, Nov 9 33°F Frost possible · Mostly Cloudy
- Tue, Nov 10 35°F Frost possible · Partly Cloudy
- Wed, Nov 11 36°F Frost possible · Mostly 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 Hamilton
The median first fall hard-freeze date (28°F) is October 2, from NOAA’s 1991–2020 Climate Normals at Hamilton. 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 25 · Jun 10 · Jun 28 | Aug 27 · Sep 9 · Sep 23 | 89 days |
| 32°F freeze | May 7 · May 21 · Jun 6 | Sep 6 · Sep 22 · Oct 5 | 122 days |
| 28°F hard freeze | Apr 20 · May 5 · May 19 | Sep 18 · Oct 2 · Oct 15 | 149 days |
Average high temperature by month
1991–2020 normals at Hamilton
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 Hamilton, MT come from the nearest weather station with freeze statistics in NOAA’s 1991–2020 Climate Normals: Hamilton (station USC00243885, elevation 3,585 ft), 0.6 mi from Hamilton. 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 Hamilton
| City | Distance | Last spring frost | First fall frost |
|---|---|---|---|
| Missoula, MT | 43 mi | May 10 | Oct 1 |
| Anaconda, MT | 50 mi | Jun 1 | Sep 14 |
| Butte, MT | 76 mi | Jun 13 | Sep 5 |
| Polson, MT | 99 mi | May 10 | Oct 5 |
| Helena, MT | 104 mi | May 9 | Sep 30 |
| Lewiston, ID | 135 mi | Apr 6 | Oct 26 |
| Kalispell, MT | 136 mi | May 31 | Sep 10 |
| Clarkston, WA | 139 mi | Apr 6 | Oct 26 |
| Moscow, ID | 139 mi | Apr 29 | Oct 2 |
| Columbia Falls, MT | 147 mi | May 31 | Sep 10 |
Frequently asked questions
When is the last frost in Hamilton?
On average, the last spring frost (32°F) in Hamilton is around May 21. In about 1 year in 10 it comes after June 6, and in 9 years in 10 it comes after May 7.
When is the first frost in Hamilton?
The first fall frost (32°F) usually arrives around September 22. There’s a 10% chance of a freeze by September 6 and a 90% chance by October 5.
Can it frost in Hamilton 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 June 10.
What growing zone is Hamilton?
Hamilton 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 59841. See growing zones in Montana.
More: all Montana frost dates · Montana growing zones · frost vs. freeze