Last spring frost
Jun 1
Frost Dates for Hayden, CO
First fall frost
Sep 20
Growing season
109 days
Hardiness zone
5a
In an average year around Hayden, CO, the last spring frost (32°F) is about Jun 1 and the first fall frost is about Sep 20, giving roughly a 109-day growing season. To be safe most years, wait until May 15 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) | Jul 3 | Jun 17 | Jun 2 |
| Freeze (32°F) | Jun 16 | Jun 1 | May 15 |
| Hard (28°F) | Jun 1 | May 13 | Apr 29 |
| Severe (24°F) | May 15 | Apr 29 | Apr 14 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Jul 3 | Jun 27 | Jun 23 | Jun 20 | Jun 17 | Jun 14 | Jun 10 | Jun 7 | Jun 2 |
| 32°F | Jun 16 | Jun 11 | Jun 7 | Jun 3 | Jun 1 | May 28 | May 25 | May 20 | May 15 |
| 28°F | Jun 1 | May 25 | May 20 | May 16 | May 13 | May 10 | May 7 | May 3 | Apr 29 |
| 24°F | May 15 | May 10 | May 6 | May 2 | Apr 29 | Apr 26 | Apr 23 | Apr 19 | Apr 14 |
| 20°F | May 3 | Apr 28 | Apr 24 | Apr 20 | Apr 15 | Apr 12 | Apr 8 | Apr 4 | Mar 30 |
| 16°F | Apr 22 | Apr 14 | Apr 9 | Apr 5 | Apr 2 | Mar 30 | Mar 25 | Mar 19 | 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) | Aug 27 | Sep 10 | Sep 22 |
| Freeze (32°F) | Sep 7 | Sep 20 | Sep 30 |
| Hard (28°F) | Sep 16 | Sep 29 | Oct 13 |
| Severe (24°F) | Sep 26 | Oct 10 | Oct 24 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Aug 27 | Sep 1 | Sep 4 | Sep 8 | Sep 10 | Sep 13 | Sep 15 | Sep 18 | Sep 22 |
| 32°F | Sep 7 | Sep 11 | Sep 14 | Sep 17 | Sep 20 | Sep 22 | Sep 25 | Sep 27 | Sep 30 |
| 28°F | Sep 16 | Sep 21 | Sep 24 | Sep 26 | Sep 29 | Oct 1 | Oct 4 | Oct 8 | Oct 13 |
| 24°F | Sep 26 | Sep 30 | Oct 3 | Oct 7 | Oct 10 | Oct 13 | Oct 16 | Oct 19 | Oct 24 |
| 20°F | Oct 5 | Oct 12 | Oct 15 | Oct 17 | Oct 20 | Oct 24 | Oct 27 | Oct 30 | Nov 4 |
| 16°F | Oct 16 | Oct 20 | Oct 24 | Oct 27 | Oct 30 | Nov 2 | Nov 5 | Nov 9 | Nov 14 |
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: Hayden, Co, about 5 miles away@if(!empty($station['elevation_ft'])), at 6,467 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 Hayden, CO?
On average, the last spring frost (32°F) around Hayden, CO is about Jun 1. In cooler years it can run later, so for a safer bet many gardeners wait until May 15.
When is the first frost in the fall?
The first fall frost around Hayden, CO typically arrives about Sep 20. 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 Jun 1 on average, or May 15 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 109 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 81639 Planting calendar → Colorado frost dates →
Data source: NOAA 1991–2020 Climate Normals · Page updated Aug 4, 2026