Last spring frost
May 13
Frost Dates for Nunn, CO
First fall frost
Sep 27
Growing season
136 days
Hardiness zone
5b
In an average year around Nunn, CO, the last spring frost (32°F) is about May 13 and the first fall frost is about Sep 27, giving roughly a 136-day growing season. To be safe most years, wait until May 2 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 6 | May 25 | May 12 |
| Freeze (32°F) | May 27 | May 13 | May 2 |
| Hard (28°F) | May 16 | May 4 | Apr 22 |
| Severe (24°F) | May 7 | Apr 25 | Apr 10 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Jun 6 | Jun 2 | May 31 | May 28 | May 25 | May 23 | May 20 | May 17 | May 12 |
| 32°F | May 27 | May 21 | May 18 | May 16 | May 13 | May 11 | May 9 | May 6 | May 2 |
| 28°F | May 16 | May 12 | May 8 | May 6 | May 4 | May 1 | Apr 29 | Apr 27 | Apr 22 |
| 24°F | May 7 | May 3 | Apr 30 | Apr 28 | Apr 25 | Apr 22 | Apr 19 | Apr 15 | Apr 10 |
| 20°F | Apr 30 | Apr 25 | Apr 20 | Apr 17 | Apr 13 | Apr 10 | Apr 7 | Apr 3 | Mar 31 |
| 16°F | Apr 19 | Apr 13 | Apr 8 | Apr 5 | Apr 2 | Mar 30 | Mar 26 | Mar 22 | Mar 14 |
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 5 | Sep 19 | Sep 30 |
| Freeze (32°F) | Sep 14 | Sep 27 | Oct 9 |
| Hard (28°F) | Sep 24 | Oct 7 | Oct 19 |
| Severe (24°F) | Oct 3 | Oct 16 | Oct 28 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Sep 5 | Sep 10 | Sep 14 | Sep 17 | Sep 19 | Sep 22 | Sep 24 | Sep 26 | Sep 30 |
| 32°F | Sep 14 | Sep 19 | Sep 23 | Sep 25 | Sep 27 | Sep 29 | Oct 2 | Oct 5 | Oct 9 |
| 28°F | Sep 24 | Sep 28 | Oct 1 | Oct 4 | Oct 7 | Oct 10 | Oct 12 | Oct 16 | Oct 19 |
| 24°F | Oct 3 | Oct 7 | Oct 10 | Oct 13 | Oct 16 | Oct 18 | Oct 22 | Oct 25 | Oct 28 |
| 20°F | Oct 11 | Oct 16 | Oct 18 | Oct 22 | Oct 25 | Oct 27 | Oct 31 | Nov 2 | Nov 8 |
| 16°F | Oct 18 | Oct 23 | Oct 26 | Oct 30 | Nov 2 | Nov 5 | Nov 8 | Nov 11 | Nov 15 |
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: Nunn 7 Nne, Co, about 6.1 miles away@if(!empty($station['elevation_ft'])), at 5,390 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 Nunn, CO?
On average, the last spring frost (32°F) around Nunn, CO is about May 13. In cooler years it can run later, so for a safer bet many gardeners wait until May 2.
When is the first frost in the fall?
The first fall frost around Nunn, CO typically arrives about Sep 27. 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 13 on average, or May 2 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 136 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 80612 Planting calendar → Colorado frost dates →
Data source: NOAA 1991–2020 Climate Normals · Page updated Aug 4, 2026