Last spring frost
Jun 12
Frost Dates for Parshall, CO
First fall frost
Sep 10
Growing season
89 days
Hardiness zone
5a
In an average year around Parshall, CO, the last spring frost (32°F) is about Jun 12 and the first fall frost is about Sep 10, giving roughly a 89-day growing season. To be safe most years, wait until May 31 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 14 | Jun 28 | Jun 16 |
| Freeze (32°F) | Jun 25 | Jun 12 | May 31 |
| Hard (28°F) | Jun 9 | May 26 | May 13 |
| Severe (24°F) | May 22 | May 9 | Apr 28 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Jul 14 | Jul 7 | Jul 3 | Jun 30 | Jun 28 | Jun 25 | Jun 22 | Jun 20 | Jun 16 |
| 32°F | Jun 25 | Jun 22 | Jun 18 | Jun 15 | Jun 12 | Jun 9 | Jun 7 | Jun 4 | May 31 |
| 28°F | Jun 9 | Jun 5 | Jun 1 | May 30 | May 26 | May 23 | May 21 | May 17 | May 13 |
| 24°F | May 22 | May 18 | May 15 | May 11 | May 9 | May 7 | May 4 | May 2 | Apr 28 |
| 20°F | May 12 | May 6 | May 2 | Apr 30 | Apr 27 | Apr 24 | Apr 20 | Apr 16 | Apr 11 |
| 16°F | May 1 | Apr 25 | Apr 20 | Apr 16 | Apr 13 | Apr 10 | Apr 7 | Apr 4 | Mar 31 |
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 13 | Aug 29 | Sep 9 |
| Freeze (32°F) | Aug 31 | Sep 10 | Sep 21 |
| Hard (28°F) | Sep 8 | Sep 20 | Oct 3 |
| Severe (24°F) | Sep 19 | Oct 1 | Oct 16 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Aug 13 | Aug 19 | Aug 23 | Aug 25 | Aug 29 | Aug 31 | Sep 2 | Sep 5 | Sep 9 |
| 32°F | Aug 31 | Sep 3 | Sep 6 | Sep 8 | Sep 10 | Sep 12 | Sep 14 | Sep 17 | Sep 21 |
| 28°F | Sep 8 | Sep 12 | Sep 15 | Sep 18 | Sep 20 | Sep 23 | Sep 25 | Sep 28 | Oct 3 |
| 24°F | Sep 19 | Sep 23 | Sep 26 | Sep 29 | Oct 1 | Oct 4 | Oct 6 | Oct 10 | Oct 16 |
| 20°F | Sep 29 | Oct 3 | Oct 6 | Oct 10 | Oct 12 | Oct 15 | Oct 18 | Oct 21 | Oct 27 |
| 16°F | Oct 8 | Oct 13 | Oct 17 | Oct 20 | Oct 23 | Oct 26 | Oct 29 | Nov 1 | Nov 6 |
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: Williams Fork Dam, Co, about 9.8 miles away@if(!empty($station['elevation_ft'])), at 7,618 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 Parshall, CO?
On average, the last spring frost (32°F) around Parshall, CO is about Jun 12. In cooler years it can run later, so for a safer bet many gardeners wait until May 31.
When is the first frost in the fall?
The first fall frost around Parshall, CO typically arrives about Sep 10. 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 31 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 89 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 80468 Planting calendar → Colorado frost dates →
Data source: NOAA 1991–2020 Climate Normals · Page updated Aug 4, 2026