Last spring frost
Apr 24
Frost Dates for Dietrich, ID
First fall frost
Oct 16
Growing season
173 days
Hardiness zone
6a
In an average year around Dietrich, ID, the last spring frost (32°F) is about Apr 24 and the first fall frost is about Oct 16, giving roughly a 173-day growing season. To be safe most years, wait until Apr 9 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) | May 31 | May 9 | Apr 24 |
| Freeze (32°F) | May 12 | Apr 24 | Apr 9 |
| Hard (28°F) | Apr 28 | Apr 9 | Mar 21 |
| Severe (24°F) | Apr 12 | Mar 20 | Mar 3 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | May 31 | May 25 | May 19 | May 14 | May 9 | May 6 | May 3 | Apr 29 | Apr 24 |
| 32°F | May 12 | May 5 | May 1 | Apr 28 | Apr 24 | Apr 21 | Apr 18 | Apr 14 | Apr 9 |
| 28°F | Apr 28 | Apr 22 | Apr 16 | Apr 12 | Apr 9 | Apr 6 | Apr 2 | Mar 30 | Mar 21 |
| 24°F | Apr 12 | Apr 4 | Mar 31 | Mar 26 | Mar 20 | Mar 15 | Mar 11 | Mar 7 | Mar 3 |
| 20°F | Mar 21 | Mar 13 | Mar 9 | Mar 6 | Mar 3 | Mar 1 | Feb 26 | Feb 21 | Feb 15 |
| 16°F | Mar 8 | Mar 3 | Feb 28 | Feb 25 | Feb 21 | Feb 17 | Feb 13 | Feb 7 | Jan 30 |
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) | Sep 22 | Oct 4 | Oct 18 |
| Freeze (32°F) | Oct 2 | Oct 16 | Nov 1 |
| Hard (28°F) | Oct 12 | Oct 26 | Nov 11 |
| Severe (24°F) | Oct 20 | Nov 6 | Nov 24 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Sep 22 | Sep 26 | Sep 29 | Oct 1 | Oct 4 | Oct 7 | Oct 10 | Oct 13 | Oct 18 |
| 32°F | Oct 2 | Oct 6 | Oct 10 | Oct 13 | Oct 16 | Oct 19 | Oct 21 | Oct 25 | Nov 1 |
| 28°F | Oct 12 | Oct 17 | Oct 20 | Oct 23 | Oct 26 | Oct 29 | Nov 1 | Nov 4 | Nov 11 |
| 24°F | Oct 20 | Oct 26 | Oct 30 | Nov 2 | Nov 6 | Nov 10 | Nov 14 | Nov 19 | Nov 24 |
| 20°F | Oct 31 | Nov 5 | Nov 10 | Nov 14 | Nov 18 | Nov 22 | Nov 26 | Nov 29 | Dec 5 |
| 16°F | Nov 8 | Nov 15 | Nov 21 | Nov 25 | Nov 28 | Dec 1 | Dec 6 | Dec 11 | Dec 19 |
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: Shoshone 1 Wnw, Id, about 9.1 miles away@if(!empty($station['elevation_ft'])), at 3,950 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 Dietrich, ID?
On average, the last spring frost (32°F) around Dietrich, ID is about Apr 24. In cooler years it can run later, so for a safer bet many gardeners wait until Apr 9.
When is the first frost in the fall?
The first fall frost around Dietrich, ID typically arrives about Oct 16. 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 Apr 24 on average, or Apr 9 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 173 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 83324 Planting calendar → Idaho frost dates →
Data source: NOAA 1991–2020 Climate Normals · Page updated Aug 4, 2026