Last spring frost
May 25
Frost Dates for Blanca, CO
First fall frost
Sep 22
Growing season
117 days
Hardiness zone
5a
In an average year around Blanca, CO, the last spring frost (32°F) is about May 25 and the first fall frost is about Sep 22, giving roughly a 117-day growing season. To be safe most years, wait until May 11 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 30 | Jun 5 | May 22 |
| Freeze (32°F) | Jun 12 | May 25 | May 11 |
| Hard (28°F) | May 31 | May 13 | Apr 29 |
| Severe (24°F) | May 17 | May 1 | Apr 18 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Jun 30 | Jun 20 | Jun 13 | Jun 9 | Jun 5 | Jun 2 | May 30 | May 27 | May 22 |
| 32°F | Jun 12 | Jun 5 | Jun 1 | May 28 | May 25 | May 22 | May 19 | May 16 | May 11 |
| 28°F | May 31 | May 23 | May 19 | May 16 | May 13 | May 10 | May 7 | May 3 | Apr 29 |
| 24°F | May 17 | May 11 | May 7 | May 3 | May 1 | Apr 29 | Apr 26 | Apr 23 | Apr 18 |
| 20°F | May 5 | May 1 | Apr 28 | Apr 23 | Apr 20 | Apr 17 | Apr 13 | Apr 9 | Apr 4 |
| 16°F | Apr 27 | Apr 19 | Apr 14 | Apr 10 | Apr 7 | Apr 4 | Mar 31 | Mar 25 | Mar 16 |
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 1 | Sep 13 | Sep 23 |
| Freeze (32°F) | Sep 10 | Sep 22 | Oct 3 |
| Hard (28°F) | Sep 16 | Oct 1 | Oct 15 |
| Severe (24°F) | Sep 26 | Oct 10 | Oct 25 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Sep 1 | Sep 5 | Sep 8 | Sep 11 | Sep 13 | Sep 15 | Sep 18 | Sep 20 | Sep 23 |
| 32°F | Sep 10 | Sep 14 | Sep 17 | Sep 20 | Sep 22 | Sep 24 | Sep 27 | Sep 30 | Oct 3 |
| 28°F | Sep 16 | Sep 22 | Sep 25 | Sep 28 | Oct 1 | Oct 3 | Oct 5 | Oct 9 | Oct 15 |
| 24°F | Sep 26 | Oct 1 | Oct 3 | Oct 6 | Oct 10 | Oct 14 | Oct 17 | Oct 20 | Oct 25 |
| 20°F | Oct 4 | Oct 9 | Oct 14 | Oct 17 | Oct 20 | Oct 23 | Oct 26 | Oct 30 | Nov 3 |
| 16°F | Oct 13 | Oct 19 | Oct 23 | Oct 26 | Oct 29 | Nov 1 | Nov 3 | Nov 6 | Nov 10 |
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: Blanca 4 Nw, Co, about 4.7 miles away@if(!empty($station['elevation_ft'])), at 7,709 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 Blanca, CO?
On average, the last spring frost (32°F) around Blanca, CO is about May 25. In cooler years it can run later, so for a safer bet many gardeners wait until May 11.
When is the first frost in the fall?
The first fall frost around Blanca, CO typically arrives about Sep 22. 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 25 on average, or May 11 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 117 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 81123 Planting calendar → Colorado frost dates →
Data source: NOAA 1991–2020 Climate Normals · Page updated Aug 4, 2026