Last spring frost
May 29
Frost Dates for Sugar City, ID
First fall frost
Sep 13
Growing season
106 days
Hardiness zone
5a
In an average year around Sugar City, ID, the last spring frost (32°F) is about May 29 and the first fall frost is about Sep 13, giving roughly a 106-day growing season. To be safe most years, wait until May 12 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 2 | Jun 17 | Jun 2 |
| Freeze (32°F) | Jun 18 | May 29 | May 12 |
| Hard (28°F) | May 27 | May 9 | Apr 27 |
| Severe (24°F) | May 9 | Apr 26 | Apr 7 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Jul 2 | Jun 28 | Jun 23 | Jun 20 | Jun 17 | Jun 13 | Jun 9 | Jun 6 | Jun 2 |
| 32°F | Jun 18 | Jun 10 | Jun 5 | Jun 1 | May 29 | May 25 | May 21 | May 17 | May 12 |
| 28°F | May 27 | May 19 | May 15 | May 12 | May 9 | May 7 | May 4 | May 1 | Apr 27 |
| 24°F | May 9 | May 5 | May 2 | Apr 29 | Apr 26 | Apr 22 | Apr 18 | Apr 13 | Apr 7 |
| 20°F | Apr 29 | Apr 24 | Apr 18 | Apr 14 | Apr 10 | Apr 5 | Apr 1 | Mar 28 | Mar 19 |
| 16°F | Apr 15 | Apr 7 | Apr 2 | Mar 30 | Mar 24 | Mar 19 | Mar 14 | Mar 11 | Mar 6 |
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 18 | Sep 2 | Sep 15 |
| Freeze (32°F) | Aug 30 | Sep 13 | Oct 1 |
| Hard (28°F) | Sep 7 | Sep 25 | Oct 13 |
| Severe (24°F) | Sep 20 | Oct 8 | Oct 28 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Aug 18 | Aug 25 | Aug 28 | Aug 31 | Sep 2 | Sep 4 | Sep 7 | Sep 10 | Sep 15 |
| 32°F | Aug 30 | Sep 3 | Sep 6 | Sep 9 | Sep 13 | Sep 16 | Sep 19 | Sep 23 | Oct 1 |
| 28°F | Sep 7 | Sep 14 | Sep 18 | Sep 22 | Sep 25 | Sep 29 | Oct 3 | Oct 7 | Oct 13 |
| 24°F | Sep 20 | Sep 26 | Oct 1 | Oct 5 | Oct 8 | Oct 13 | Oct 17 | Oct 21 | Oct 28 |
| 20°F | Oct 1 | Oct 9 | Oct 16 | Oct 19 | Oct 23 | Oct 27 | Oct 30 | Nov 3 | Nov 11 |
| 16°F | Oct 19 | Oct 24 | Oct 28 | Nov 1 | Nov 4 | Nov 9 | Nov 13 | Nov 19 | Nov 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: Sugar City, Id, about 2.9 miles away@if(!empty($station['elevation_ft'])), at 4,925 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 Sugar City, ID?
On average, the last spring frost (32°F) around Sugar City, ID is about May 29. In cooler years it can run later, so for a safer bet many gardeners wait until May 12.
When is the first frost in the fall?
The first fall frost around Sugar City, ID typically arrives about Sep 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 May 29 on average, or May 12 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 106 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 83448 Planting calendar → Idaho frost dates →
Data source: NOAA 1991–2020 Climate Normals · Page updated Aug 4, 2026