Last spring frost
Jun 12
Frost Dates for Sinclair, WY
First fall frost
Sep 7
Growing season
83 days
Hardiness zone
5a
In an average year around Sinclair, WY, the last spring frost (32°F) is about Jun 12 and the first fall frost is about Sep 7, giving roughly a 83-day growing season. To be safe most years, wait until May 25 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%) |
|---|---|---|---|
| Freeze (32°F) | Jun 30 | Jun 12 | May 25 |
| Hard (28°F) | Jun 16 | May 25 | May 9 |
| Severe (24°F) | May 28 | May 9 | Apr 27 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 32°F | Jun 30 | Jun 24 | Jun 19 | Jun 15 | Jun 12 | Jun 7 | Jun 3 | May 31 | May 25 |
| 28°F | Jun 16 | Jun 6 | Jun 2 | May 30 | May 25 | May 22 | May 18 | May 14 | May 9 |
| 24°F | May 28 | May 20 | May 15 | May 12 | May 9 | May 6 | May 3 | May 1 | Apr 27 |
| 20°F | May 13 | May 8 | May 4 | May 1 | Apr 29 | Apr 25 | Apr 21 | Apr 16 | Apr 11 |
| 16°F | May 2 | Apr 28 | Apr 24 | Apr 19 | Apr 15 | Apr 11 | Apr 7 | Apr 3 | Mar 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%) |
|---|---|---|---|
| Freeze (32°F) | Aug 22 | Sep 7 | Sep 19 |
| Hard (28°F) | Sep 1 | Sep 16 | Sep 30 |
| Severe (24°F) | Sep 12 | Sep 27 | Oct 11 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 32°F | Aug 22 | Aug 28 | Sep 1 | Sep 4 | Sep 7 | Sep 10 | Sep 12 | Sep 15 | Sep 19 |
| 28°F | Sep 1 | Sep 7 | Sep 10 | Sep 13 | Sep 16 | Sep 19 | Sep 21 | Sep 25 | Sep 30 |
| 24°F | Sep 12 | Sep 16 | Sep 21 | Sep 24 | Sep 27 | Sep 30 | Oct 3 | Oct 6 | Oct 11 |
| 20°F | Sep 23 | Sep 27 | Oct 1 | Oct 4 | Oct 7 | Oct 11 | Oct 14 | Oct 18 | Oct 23 |
| 16°F | Oct 3 | Oct 9 | Oct 13 | Oct 16 | Oct 18 | Oct 22 | Oct 25 | Oct 29 | Nov 2 |
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: Saratoga 4N, Wy, about 17.9 miles away@if(!empty($station['elevation_ft'])), at 6,801 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 Sinclair, WY?
On average, the last spring frost (32°F) around Sinclair, WY is about Jun 12. In cooler years it can run later, so for a safer bet many gardeners wait until May 25.
When is the first frost in the fall?
The first fall frost around Sinclair, WY typically arrives about Sep 7. 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 Jun 12 on average, or May 25 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 83 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 82335 Planting calendar → Wyoming frost dates →
Data source: NOAA 1991–2020 Climate Normals · Page updated Aug 4, 2026