Last spring frost
May 1
Frost Dates for Hartman, CO
First fall frost
Oct 12
Growing season
163 days
Hardiness zone
6a
In an average year around Hartman, CO, the last spring frost (32°F) is about May 1 and the first fall frost is about Oct 12, giving roughly a 163-day growing season. To be safe most years, wait until Apr 18 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) | May 25 | May 10 | Apr 30 |
| Freeze (32°F) | May 14 | May 1 | Apr 18 |
| Hard (28°F) | May 4 | Apr 21 | Apr 7 |
| Severe (24°F) | Apr 25 | Apr 10 | Mar 25 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | May 25 | May 19 | May 16 | May 13 | May 10 | May 8 | May 6 | May 3 | Apr 30 |
| 32°F | May 14 | May 9 | May 6 | May 4 | May 1 | Apr 30 | Apr 26 | Apr 22 | Apr 18 |
| 28°F | May 4 | Apr 30 | Apr 27 | Apr 24 | Apr 21 | Apr 18 | Apr 16 | Apr 13 | Apr 7 |
| 24°F | Apr 25 | Apr 21 | Apr 17 | Apr 14 | Apr 10 | Apr 7 | Apr 4 | Mar 31 | Mar 25 |
| 20°F | Apr 17 | Apr 10 | Apr 6 | Apr 3 | Mar 31 | Mar 27 | Mar 22 | Mar 15 | Mar 9 |
| 16°F | Apr 6 | Apr 1 | Mar 26 | Mar 20 | Mar 15 | Mar 10 | Mar 6 | Mar 2 | Feb 26 |
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 23 | Oct 3 | Oct 15 |
| Freeze (32°F) | Sep 29 | Oct 12 | Oct 23 |
| Hard (28°F) | Oct 7 | Oct 21 | Nov 2 |
| Severe (24°F) | Oct 18 | Oct 30 | Nov 11 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Sep 23 | Sep 26 | Sep 29 | Oct 1 | Oct 3 | Oct 5 | Oct 8 | Oct 11 | Oct 15 |
| 32°F | Sep 29 | Oct 3 | Oct 6 | Oct 9 | Oct 12 | Oct 15 | Oct 17 | Oct 20 | Oct 23 |
| 28°F | Oct 7 | Oct 12 | Oct 16 | Oct 18 | Oct 21 | Oct 23 | Oct 25 | Oct 28 | Nov 2 |
| 24°F | Oct 18 | Oct 22 | Oct 25 | Oct 27 | Oct 30 | Nov 1 | Nov 4 | Nov 7 | Nov 11 |
| 20°F | Oct 25 | Oct 30 | Nov 2 | Nov 4 | Nov 7 | Nov 9 | Nov 13 | Nov 17 | Nov 21 |
| 16°F | Nov 1 | Nov 5 | Nov 9 | Nov 12 | Nov 15 | Nov 18 | Nov 21 | 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: Holly, Co, about 6.8 miles away@if(!empty($station['elevation_ft'])), at 3,401 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 Hartman, CO?
On average, the last spring frost (32°F) around Hartman, CO is about May 1. In cooler years it can run later, so for a safer bet many gardeners wait until Apr 18.
When is the first frost in the fall?
The first fall frost around Hartman, CO typically arrives about Oct 12. 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 1 on average, or Apr 18 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 163 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 81043 Planting calendar → Colorado frost dates →
Data source: NOAA 1991–2020 Climate Normals · Page updated Aug 4, 2026