Last spring frost
May 17
Frost Dates for Air Force Academy, CO
First fall frost
Oct 1
Growing season
136 days
Hardiness zone
5b
In an average year around Air Force Academy, CO, the last spring frost (32°F) is about May 17 and the first fall frost is about Oct 1, giving roughly a 136-day growing season. To be safe most years, wait until May 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%) |
|---|---|---|---|
| Light (36°F) | Jun 12 | May 29 | May 16 |
| Freeze (32°F) | May 30 | May 17 | May 5 |
| Hard (28°F) | May 20 | May 6 | Apr 26 |
| Severe (24°F) | May 10 | Apr 29 | Apr 14 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Jun 12 | Jun 7 | Jun 3 | May 31 | May 29 | May 26 | May 23 | May 20 | May 16 |
| 32°F | May 30 | May 25 | May 22 | May 19 | May 17 | May 14 | May 12 | May 8 | May 5 |
| 28°F | May 20 | May 15 | May 11 | May 9 | May 6 | May 4 | May 2 | Apr 30 | Apr 26 |
| 24°F | May 10 | May 6 | May 3 | Apr 30 | Apr 29 | Apr 26 | Apr 22 | Apr 19 | Apr 14 |
| 20°F | May 1 | Apr 27 | Apr 23 | Apr 19 | Apr 17 | Apr 13 | Apr 8 | Apr 4 | Mar 31 |
| 16°F | Apr 22 | Apr 16 | Apr 11 | Apr 6 | Apr 3 | Mar 31 | Mar 27 | Mar 22 | Mar 15 |
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 9 | Sep 23 | Oct 2 |
| Freeze (32°F) | Sep 19 | Oct 1 | Oct 12 |
| Hard (28°F) | Sep 28 | Oct 9 | Oct 20 |
| Severe (24°F) | Oct 5 | Oct 17 | Oct 29 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Sep 9 | Sep 14 | Sep 17 | Sep 21 | Sep 23 | Sep 25 | Sep 27 | Sep 30 | Oct 2 |
| 32°F | Sep 19 | Sep 24 | Sep 27 | Sep 29 | Oct 1 | Oct 3 | Oct 5 | Oct 8 | Oct 12 |
| 28°F | Sep 28 | Oct 2 | Oct 4 | Oct 7 | Oct 9 | Oct 12 | Oct 14 | Oct 17 | Oct 20 |
| 24°F | Oct 5 | Oct 9 | Oct 12 | Oct 15 | Oct 17 | Oct 19 | Oct 21 | Oct 24 | Oct 29 |
| 20°F | Oct 12 | Oct 16 | Oct 19 | Oct 22 | Oct 25 | Oct 28 | Oct 31 | Nov 3 | Nov 8 |
| 16°F | Oct 19 | Oct 23 | Oct 28 | Oct 31 | Nov 3 | Nov 6 | Nov 9 | Nov 13 | Nov 18 |
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: Monument 3S, Co, about 3.9 miles away@if(!empty($station['elevation_ft'])), at 6,821 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 Air Force Academy, CO?
On average, the last spring frost (32°F) around Air Force Academy, CO is about May 17. In cooler years it can run later, so for a safer bet many gardeners wait until May 5.
When is the first frost in the fall?
The first fall frost around Air Force Academy, CO typically arrives about Oct 1. 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 17 on average, or May 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 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 80840 Planting calendar → Colorado frost dates →
Data source: NOAA 1991–2020 Climate Normals · Page updated Aug 4, 2026