Last spring frost
Jun 20
Frost Dates for Kelly, WY
First fall frost
Aug 31
Growing season
70 days
Hardiness zone
5a
In an average year around Kelly, WY, the last spring frost (32°F) is about Jun 20 and the first fall frost is about Aug 31, giving roughly a 70-day growing season. To be safe most years, wait until Jun 5 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) | Jul 9 | Jun 20 | Jun 5 |
| Hard (28°F) | Jun 21 | Jun 2 | May 12 |
| Severe (24°F) | Jun 2 | May 12 | Apr 29 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 32°F | Jul 9 | Jul 1 | Jun 27 | Jun 24 | Jun 20 | Jun 18 | Jun 15 | Jun 11 | Jun 5 |
| 28°F | Jun 21 | Jun 16 | Jun 11 | Jun 7 | Jun 2 | May 28 | May 23 | May 18 | May 12 |
| 24°F | Jun 2 | May 24 | May 19 | May 15 | May 12 | May 8 | May 5 | May 2 | Apr 29 |
| 20°F | May 12 | May 7 | May 3 | May 1 | Apr 29 | Apr 26 | Apr 23 | Apr 20 | Apr 15 |
| 16°F | May 1 | Apr 28 | Apr 24 | Apr 21 | Apr 19 | Apr 16 | Apr 12 | Apr 9 | Apr 5 |
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 12 | Aug 31 | Sep 13 |
| Hard (28°F) | Aug 30 | Sep 13 | Sep 30 |
| Severe (24°F) | Sep 12 | Sep 27 | Oct 12 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 32°F | Aug 12 | Aug 20 | Aug 25 | Aug 28 | Aug 31 | Sep 3 | Sep 5 | Sep 9 | Sep 13 |
| 28°F | Aug 30 | Sep 4 | Sep 7 | Sep 10 | Sep 13 | Sep 17 | Sep 20 | Sep 25 | Sep 30 |
| 24°F | Sep 12 | Sep 17 | Sep 21 | Sep 24 | Sep 27 | Sep 30 | Oct 3 | Oct 7 | Oct 12 |
| 20°F | Sep 22 | Sep 27 | Oct 1 | Oct 5 | Oct 8 | Oct 12 | Oct 15 | Oct 18 | Oct 23 |
| 16°F | Oct 1 | Oct 7 | Oct 12 | Oct 17 | Oct 21 | Oct 24 | Oct 27 | Oct 30 | Nov 3 |
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: Moose, Wy, about 10.2 miles away@if(!empty($station['elevation_ft'])), at 6,444 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 Kelly, WY?
On average, the last spring frost (32°F) around Kelly, WY is about Jun 20. In cooler years it can run later, so for a safer bet many gardeners wait until Jun 5.
When is the first frost in the fall?
The first fall frost around Kelly, WY typically arrives about Aug 31. 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 20 on average, or Jun 5 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 70 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 83011 Planting calendar → Wyoming frost dates →
Data source: NOAA 1991–2020 Climate Normals · Page updated Aug 4, 2026