Last spring frost
Apr 29
Frost Dates for Nampa, ID
First fall frost
Oct 13
Growing season
164 days
Hardiness zone
7a
In an average year around Nampa, ID, the last spring frost (32°F) is about Apr 29 and the first fall frost is about Oct 13, giving roughly a 164-day growing season. To be safe most years, wait until Apr 15 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 6 | May 16 | May 1 |
| Freeze (32°F) | May 18 | Apr 29 | Apr 15 |
| Hard (28°F) | May 1 | Apr 11 | Mar 25 |
| Severe (24°F) | Apr 12 | Mar 22 | Mar 2 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Jun 6 | May 31 | May 24 | May 20 | May 16 | May 13 | May 10 | May 6 | May 1 |
| 32°F | May 18 | May 9 | May 5 | May 1 | Apr 29 | Apr 27 | Apr 23 | Apr 20 | Apr 15 |
| 28°F | May 1 | Apr 25 | Apr 20 | Apr 16 | Apr 11 | Apr 8 | Apr 4 | Mar 31 | Mar 25 |
| 24°F | Apr 12 | Apr 6 | Apr 1 | Mar 28 | Mar 22 | Mar 17 | Mar 12 | Mar 8 | Mar 2 |
| 20°F | Mar 26 | Mar 13 | Mar 9 | Mar 4 | Feb 28 | Feb 26 | Feb 21 | Feb 16 | Feb 8 |
| 16°F | Mar 3 | Feb 25 | Feb 21 | Feb 16 | Feb 11 | Feb 6 | Jan 31 | Jan 22 | Jan 7 |
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 15 | Sep 30 | Oct 14 |
| Freeze (32°F) | Sep 29 | Oct 13 | Oct 28 |
| Hard (28°F) | Oct 9 | Oct 25 | Nov 10 |
| Severe (24°F) | Oct 22 | Nov 6 | Nov 24 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Sep 15 | Sep 20 | Sep 24 | Sep 27 | Sep 30 | Oct 2 | Oct 5 | Oct 8 | Oct 14 |
| 32°F | Sep 29 | Oct 3 | Oct 6 | Oct 9 | Oct 13 | Oct 16 | Oct 19 | Oct 22 | Oct 28 |
| 28°F | Oct 9 | Oct 15 | Oct 18 | Oct 22 | Oct 25 | Oct 28 | Nov 1 | Nov 4 | Nov 10 |
| 24°F | Oct 22 | Oct 27 | Nov 1 | Nov 3 | Nov 6 | Nov 10 | Nov 14 | Nov 19 | Nov 24 |
| 20°F | Oct 31 | Nov 6 | Nov 11 | Nov 15 | Nov 19 | Nov 23 | Nov 26 | Nov 30 | Dec 5 |
| 16°F | Nov 9 | Nov 16 | Nov 23 | Nov 27 | Dec 1 | Dec 4 | Dec 8 | Dec 14 | Dec 24 |
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: Nampa Sugar Factory, Id, about 7.4 miles away@if(!empty($station['elevation_ft'])), at 2,470 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 Nampa, ID?
On average, the last spring frost (32°F) around Nampa, ID is about Apr 29. In cooler years it can run later, so for a safer bet many gardeners wait until Apr 15.
When is the first frost in the fall?
The first fall frost around Nampa, ID typically arrives about Oct 13. 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 29 on average, or Apr 15 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 164 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 83686 Planting calendar → Idaho frost dates →
Data source: NOAA 1991–2020 Climate Normals · Page updated Aug 4, 2026