Last spring frost
May 26
Frost Dates for Willow Creek, MT
First fall frost
Sep 15
Growing season
111 days
Hardiness zone
5a
In an average year around Willow Creek, MT, the last spring frost (32°F) is about May 26 and the first fall frost is about Sep 15, giving roughly a 111-day growing season. To be safe most years, wait until May 11 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%) |
|---|---|---|---|
| Light (36°F) | Jul 3 | Jun 12 | May 29 |
| Freeze (32°F) | Jun 12 | May 26 | May 11 |
| Hard (28°F) | May 27 | May 11 | Apr 29 |
| Severe (24°F) | May 15 | Apr 30 | Apr 14 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Jul 3 | Jun 24 | Jun 19 | Jun 16 | Jun 12 | Jun 9 | Jun 5 | Jun 2 | May 29 |
| 32°F | Jun 12 | Jun 4 | Jun 1 | May 29 | May 26 | May 23 | May 19 | May 16 | May 11 |
| 28°F | May 27 | May 21 | May 17 | May 13 | May 11 | May 8 | May 5 | May 3 | Apr 29 |
| 24°F | May 15 | May 9 | May 5 | May 2 | Apr 30 | Apr 28 | Apr 24 | Apr 20 | Apr 14 |
| 20°F | May 3 | Apr 29 | Apr 24 | Apr 21 | Apr 17 | Apr 13 | Apr 10 | Apr 6 | Apr 2 |
| 16°F | Apr 24 | Apr 17 | Apr 12 | Apr 7 | Apr 4 | Apr 1 | Mar 29 | Mar 23 | Mar 15 |
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%) |
|---|---|---|---|
| Light (36°F) | Aug 17 | Sep 3 | Sep 16 |
| Freeze (32°F) | Sep 1 | Sep 15 | Sep 28 |
| Hard (28°F) | Sep 12 | Sep 27 | Oct 8 |
| Severe (24°F) | Sep 23 | Oct 5 | Oct 18 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Aug 17 | Aug 24 | Aug 29 | Sep 1 | Sep 3 | Sep 6 | Sep 9 | Sep 12 | Sep 16 |
| 32°F | Sep 1 | Sep 6 | Sep 9 | Sep 12 | Sep 15 | Sep 17 | Sep 21 | Sep 24 | Sep 28 |
| 28°F | Sep 12 | Sep 18 | Sep 22 | Sep 25 | Sep 27 | Sep 29 | Oct 1 | Oct 4 | Oct 8 |
| 24°F | Sep 23 | Sep 28 | Oct 1 | Oct 3 | Oct 5 | Oct 8 | Oct 11 | Oct 14 | Oct 18 |
| 20°F | Oct 1 | Oct 5 | Oct 9 | Oct 13 | Oct 16 | Oct 20 | Oct 23 | Oct 26 | Oct 30 |
| 16°F | Oct 9 | Oct 15 | Oct 20 | Oct 23 | Oct 26 | Oct 29 | Nov 1 | Nov 4 | Nov 9 |
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: Logan Landfill, Mt, about 12 miles away@if(!empty($station['elevation_ft'])), at 4,243 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 Willow Creek, MT?
On average, the last spring frost (32°F) around Willow Creek, MT is about May 26. In cooler years it can run later, so for a safer bet many gardeners wait until May 11.
When is the first frost in the fall?
The first fall frost around Willow Creek, 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 May 26 on average, or May 11 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 111 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 59760 Planting calendar → Montana frost dates →
Data source: NOAA 1991–2020 Climate Normals · Page updated Aug 4, 2026