Last spring frost
May 16
Frost Dates for Roxborough Park, CO
First fall frost
Sep 29
Growing season
132 days
Hardiness zone
5b
In an average year around Roxborough Park, CO, the last spring frost (32°F) is about May 16 and the first fall frost is about Sep 29, giving roughly a 132-day growing season. To be safe most years, wait until May 3 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 16 | Jun 1 | May 17 |
| Freeze (32°F) | Jun 6 | May 16 | May 3 |
| Hard (28°F) | May 19 | May 3 | Apr 21 |
| Severe (24°F) | May 7 | Apr 23 | Apr 7 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Jun 16 | Jun 11 | Jun 8 | Jun 4 | Jun 1 | May 30 | May 26 | May 22 | May 17 |
| 32°F | Jun 6 | May 31 | May 25 | May 21 | May 16 | May 13 | May 10 | May 8 | May 3 |
| 28°F | May 19 | May 12 | May 9 | May 6 | May 3 | May 1 | Apr 29 | Apr 26 | Apr 21 |
| 24°F | May 7 | May 1 | Apr 29 | Apr 25 | Apr 23 | Apr 20 | Apr 16 | Apr 13 | Apr 7 |
| 20°F | Apr 28 | Apr 23 | Apr 19 | Apr 15 | Apr 12 | Apr 8 | Apr 4 | Apr 1 | Mar 24 |
| 16°F | Apr 20 | Apr 13 | Apr 8 | Apr 4 | Apr 1 | Mar 28 | Mar 22 | Mar 17 | Mar 11 |
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 8 | Sep 21 | Oct 1 |
| Freeze (32°F) | Sep 16 | Sep 29 | Oct 11 |
| Hard (28°F) | Sep 25 | Oct 8 | Oct 22 |
| Severe (24°F) | Oct 4 | Oct 17 | Nov 2 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Sep 8 | Sep 13 | Sep 16 | Sep 18 | Sep 21 | Sep 23 | Sep 25 | Sep 27 | Oct 1 |
| 32°F | Sep 16 | Sep 21 | Sep 24 | Sep 27 | Sep 29 | Oct 1 | Oct 4 | Oct 7 | Oct 11 |
| 28°F | Sep 25 | Oct 1 | Oct 3 | Oct 5 | Oct 8 | Oct 11 | Oct 14 | Oct 17 | Oct 22 |
| 24°F | Oct 4 | Oct 8 | Oct 12 | Oct 15 | Oct 17 | Oct 21 | Oct 24 | Oct 29 | Nov 2 |
| 20°F | Oct 10 | Oct 16 | Oct 21 | Oct 25 | Oct 29 | Nov 1 | Nov 4 | Nov 8 | Nov 14 |
| 16°F | Oct 18 | Oct 25 | Oct 30 | Nov 3 | Nov 7 | Nov 11 | Nov 15 | Nov 19 | Nov 23 |
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: Strontia Springs Dam, Co, about 7.4 miles away@if(!empty($station['elevation_ft'])), at 5,840 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 Roxborough Park, CO?
On average, the last spring frost (32°F) around Roxborough Park, CO is about May 16. In cooler years it can run later, so for a safer bet many gardeners wait until May 3.
When is the first frost in the fall?
The first fall frost around Roxborough Park, CO typically arrives about Sep 29. 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 16 on average, or May 3 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 132 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 80425 Planting calendar → Colorado frost dates →
Data source: NOAA 1991–2020 Climate Normals · Page updated Aug 4, 2026