Last spring frost
Jun 1
Frost Dates for Judith Gap, MT
First fall frost
Sep 15
Growing season
104 days
Hardiness zone
4b
In an average year around Judith Gap, MT, the last spring frost (32°F) is about Jun 1 and the first fall frost is about Sep 15, giving roughly a 104-day growing season. To be safe most years, wait until May 17 before setting out tender plants.
Last spring frost
Dates the last frost of spring typically ends. Plant tender crops after the risk has passed for your comfort level.
| Frost intensity | Early (10%) | Average (50%) | Late (90%) |
|---|---|---|---|
| Freeze (32°F) | Jun 16 | Jun 1 | May 17 |
| Hard (28°F) | May 31 | May 15 | May 3 |
| Severe (24°F) | May 16 | May 2 | Apr 17 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 32°F | Jun 16 | Jun 11 | Jun 7 | Jun 4 | Jun 1 | May 29 | May 25 | May 21 | May 17 |
| 28°F | May 31 | May 25 | May 20 | May 17 | May 15 | May 12 | May 10 | May 7 | May 3 |
| 24°F | May 16 | May 10 | May 7 | May 5 | May 2 | Apr 30 | Apr 27 | Apr 24 | Apr 17 |
| 20°F | May 5 | May 1 | Apr 28 | Apr 25 | Apr 21 | Apr 18 | Apr 14 | Apr 8 | Apr 3 |
| 16°F | Apr 27 | Apr 22 | Apr 18 | Apr 13 | Apr 7 | Apr 4 | Apr 1 | Mar 28 | Mar 19 |
First fall frost
Dates the first frost of fall typically arrives. Count back by a crop's days-to-maturity to know your planting cutoff.
| Frost intensity | Early (10%) | Average (50%) | Late (90%) |
|---|---|---|---|
| Freeze (32°F) | Aug 31 | Sep 15 | Sep 28 |
| Hard (28°F) | Sep 11 | Sep 28 | Oct 9 |
| Severe (24°F) | Sep 22 | Oct 7 | Oct 20 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 32°F | Aug 31 | Sep 5 | Sep 10 | Sep 13 | Sep 15 | Sep 18 | Sep 21 | Sep 24 | Sep 28 |
| 28°F | Sep 11 | Sep 17 | Sep 23 | Sep 26 | Sep 28 | Sep 30 | Oct 2 | Oct 5 | Oct 9 |
| 24°F | Sep 22 | Sep 29 | Oct 1 | Oct 4 | Oct 7 | Oct 10 | Oct 13 | Oct 16 | Oct 20 |
| 20°F | Oct 1 | Oct 6 | Oct 10 | Oct 14 | Oct 16 | Oct 19 | Oct 22 | Oct 25 | Oct 31 |
| 16°F | Oct 7 | Oct 14 | Oct 18 | Oct 21 | Oct 25 | Oct 28 | Nov 1 | Nov 5 | Nov 11 |
Growing season is measured at 32°F with about 50% probability. Hardiness zone from the 2023 USDA map; frost normals from NOAA 1991-2020.
Where this data comes from
@endif These dates are computed from the nearest official weather station with long-term records: Judith Gap, Mt, about 10 miles away@if(!empty($station['elevation_ft'])), at 4,630 ft elevation. The further the station and the greater the elevation difference from your yard, the more your local frost timing can vary.
How we calculate these dates
Frost and freeze dates come from the NOAA 1991–2020 U.S. Climate Normals, the National Oceanic and Atmospheric Administration's 30-year averages for each weather station. A date shown at the 50% level is the median: in half of years the frost falls on or before it. The 10% and 90% columns show the early and late ends of the range, so you can plant on the odds you're comfortable with. These are long-term averages, not a forecast for this year - always check your local outlook before planting.
Source: NOAA National Centers for Environmental Information, 1991–2020 Climate Normals (public domain). Harman is not affiliated with or endorsed by NOAA.
Frequently asked questions
When is the last frost in Judith Gap, MT?
On average, the last spring frost (32°F) around Judith Gap, MT is about Jun 1. In cooler years it can run later, so for a safer bet many gardeners wait until May 17.
When is the first frost in the fall?
The first fall frost around Judith Gap, MT typically arrives about Sep 15. Count back by a crop's days to maturity to find the latest date you can plant it.
When can I plant tomatoes and other tender crops?
Tender crops like tomatoes, peppers and basil are damaged by frost, so wait until the last spring frost has passed - around Jun 1 on average, or May 17 to be safe most years.
How long is the growing season here?
The frost-free growing season (between the last spring and first fall 32°F frost) is about 104 days in a typical year.
Are these dates a forecast for this year?
No. They are 30-year averages from the NOAA 1991–2020 Climate Normals, not a prediction for the current year. Use them for planning and always check your local weather forecast before planting or protecting crops.
Local weather for 59418 Planting calendar → Montana frost dates →
Data source: NOAA 1991–2020 Climate Normals · Page updated Aug 4, 2026