Last spring frost
May 9
Frost Dates for Lewisville, ID
First fall frost
Oct 5
Growing season
148 days
Hardiness zone
5a
In an average year around Lewisville, ID, the last spring frost (32°F) is about May 9 and the first fall frost is about Oct 5, giving roughly a 148-day growing season. To be safe most years, wait until Apr 27 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 14 | May 26 | May 10 |
| Freeze (32°F) | May 25 | May 9 | Apr 27 |
| Hard (28°F) | May 11 | Apr 28 | Apr 12 |
| Severe (24°F) | Apr 30 | Apr 13 | Mar 24 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Jun 14 | Jun 8 | Jun 4 | May 31 | May 26 | May 23 | May 19 | May 16 | May 10 |
| 32°F | May 25 | May 19 | May 15 | May 12 | May 9 | May 6 | May 3 | May 1 | Apr 27 |
| 28°F | May 11 | May 6 | May 2 | Apr 30 | Apr 28 | Apr 24 | Apr 21 | Apr 17 | Apr 12 |
| 24°F | Apr 30 | Apr 25 | Apr 19 | Apr 16 | Apr 13 | Apr 9 | Apr 6 | Apr 1 | Mar 24 |
| 20°F | Apr 17 | Apr 11 | Apr 6 | Apr 2 | Mar 30 | Mar 24 | Mar 17 | Mar 13 | Mar 8 |
| 16°F | Apr 1 | Mar 24 | Mar 16 | Mar 13 | Mar 9 | Mar 7 | Mar 5 | Mar 2 | Feb 27 |
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 9 | Sep 24 | Oct 6 |
| Freeze (32°F) | Sep 21 | Oct 5 | Oct 18 |
| Hard (28°F) | Oct 2 | Oct 16 | Oct 28 |
| Severe (24°F) | Oct 11 | Oct 25 | Nov 9 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Sep 9 | Sep 14 | Sep 19 | Sep 21 | Sep 24 | Sep 27 | Sep 30 | Oct 3 | Oct 6 |
| 32°F | Sep 21 | Sep 27 | Sep 30 | Oct 2 | Oct 5 | Oct 6 | Oct 10 | Oct 14 | Oct 18 |
| 28°F | Oct 2 | Oct 6 | Oct 9 | Oct 13 | Oct 16 | Oct 18 | Oct 21 | Oct 25 | Oct 28 |
| 24°F | Oct 11 | Oct 16 | Oct 20 | Oct 23 | Oct 25 | Oct 28 | Oct 31 | Nov 3 | Nov 9 |
| 20°F | Oct 21 | Oct 25 | Oct 29 | Nov 1 | Nov 4 | Nov 7 | Nov 11 | Nov 15 | Nov 21 |
| 16°F | Oct 29 | Nov 3 | Nov 6 | Nov 11 | Nov 14 | Nov 18 | Nov 22 | Nov 25 | Nov 29 |
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: Rigby, Id, about 6.1 miles away@if(!empty($station['elevation_ft'])), at 4,856 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 Lewisville, ID?
On average, the last spring frost (32°F) around Lewisville, ID is about May 9. In cooler years it can run later, so for a safer bet many gardeners wait until Apr 27.
When is the first frost in the fall?
The first fall frost around Lewisville, ID typically arrives about Oct 5. 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 9 on average, or Apr 27 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 148 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 83431 Planting calendar → Idaho frost dates →
Data source: NOAA 1991–2020 Climate Normals · Page updated Aug 4, 2026