Last spring frost
May 12
Frost Dates for Rexburg, ID
First fall frost
Sep 24
Growing season
132 days
Hardiness zone
5a
In an average year around Rexburg, ID, the last spring frost (32°F) is about May 12 and the first fall frost is about Sep 24, giving roughly a 132-day growing season. To be safe most years, wait until Apr 29 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) | Jun 22 | Jun 4 | May 16 |
| Freeze (32°F) | Jun 2 | May 12 | Apr 29 |
| Hard (28°F) | May 14 | Apr 30 | Apr 12 |
| Severe (24°F) | May 4 | Apr 15 | Mar 29 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Jun 22 | Jun 16 | Jun 11 | Jun 8 | Jun 4 | May 31 | May 27 | May 22 | May 16 |
| 32°F | Jun 2 | May 27 | May 20 | May 15 | May 12 | May 9 | May 6 | May 3 | Apr 29 |
| 28°F | May 14 | May 9 | May 5 | May 2 | Apr 30 | Apr 26 | Apr 23 | Apr 18 | Apr 12 |
| 24°F | May 4 | Apr 27 | Apr 23 | Apr 19 | Apr 15 | Apr 11 | Apr 7 | Apr 3 | Mar 29 |
| 20°F | Apr 20 | Apr 13 | Apr 6 | Apr 3 | Mar 30 | Mar 27 | Mar 22 | Mar 17 | Mar 11 |
| 16°F | Apr 5 | Mar 30 | Mar 24 | Mar 19 | Mar 16 | Mar 12 | Mar 9 | Mar 6 | Mar 1 |
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 28 | Sep 11 | Sep 25 |
| Freeze (32°F) | Sep 6 | Sep 24 | Oct 8 |
| Hard (28°F) | Sep 20 | Oct 7 | Oct 21 |
| Severe (24°F) | Oct 2 | Oct 20 | Nov 4 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Aug 28 | Sep 2 | Sep 5 | Sep 8 | Sep 11 | Sep 14 | Sep 17 | Sep 21 | Sep 25 |
| 32°F | Sep 6 | Sep 12 | Sep 17 | Sep 21 | Sep 24 | Sep 27 | Oct 1 | Oct 4 | Oct 8 |
| 28°F | Sep 20 | Sep 27 | Oct 1 | Oct 4 | Oct 7 | Oct 10 | Oct 13 | Oct 17 | Oct 21 |
| 24°F | Oct 2 | Oct 8 | Oct 12 | Oct 17 | Oct 20 | Oct 23 | Oct 26 | Oct 30 | Nov 4 |
| 20°F | Oct 15 | Oct 20 | Oct 24 | Oct 28 | Oct 31 | Nov 3 | Nov 7 | Nov 12 | Nov 17 |
| 16°F | Oct 25 | Oct 31 | Nov 2 | Nov 7 | Nov 11 | Nov 14 | Nov 18 | Nov 22 | Nov 28 |
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: Rexburg Byu Idaho, Id, about 1 miles away@if(!empty($station['elevation_ft'])), at 5,005 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 Rexburg, ID?
On average, the last spring frost (32°F) around Rexburg, ID is about May 12. In cooler years it can run later, so for a safer bet many gardeners wait until Apr 29.
When is the first frost in the fall?
The first fall frost around Rexburg, ID typically arrives about Sep 24. 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 12 on average, or Apr 29 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 132 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 83440 Planting calendar → Idaho frost dates →
Data source: NOAA 1991–2020 Climate Normals · Page updated Aug 4, 2026