USDA Hardiness Zone 6a
Frost Dates for 81326 — Hesperus, Colorado
NOAA 1991–2020 normals from Fort Lewis, CO (7,614 ft), 9 miles northeast.
Updated
In Hesperus, the last spring frost (32°F) is around June 1 in half of years and has passed by June 19 in nine years out of ten. The first fall frost comes around September 27, as early as September 13 one year in ten, leaving a typical freeze-free season of 116 days (NOAA, Fort Lewis, CO).
- Last spring frost
- June 1
- First fall frost
- September 27
- Growing season
- 116 days
- Hardiness zone
- 6a
50% probability
50% probability
freeze-free, 50%
-10 to -5°F (-23.3 to -20.6°C) coldest night
- First snow
- November 11
- Last snow
- April 20
- Winters with snow
- 100%
- Snow per year
- —
median, 1991–2020
median, 1991–2020
16 of 16 observed
NOAA normal
Frost risk by date in Hesperus
Half of springs at Fort Lewis, CO see their last 32°F night by June 1; only one in ten is past it by May 16, and one in ten still has one after June 19. Planting tender crops after June 8 leaves a 30% risk of a frost on them, after June 13 20%, and after June 19 10%. The 18 days between the even-odds date and the one-in-ten date is wider than at 89% of the 110 Colorado stations behind this site's ZIP pages.
In fall the first 32°F night comes by September 27 in half of years, as early as September 13 one year in ten, and holds off past October 8 one year in ten. A hard freeze of 28°F follows 9 days later, around October 6; in spring the one-in-ten date for 28°F is June 8, 11 days before the 32°F one. The freeze-free season lasts 116 days in a typical year, shorter than at 69% of the 110 Colorado stations; it reaches 136 days one year in ten and falls short of 95 one year in ten. On average 205 nights a year drop to 32°F or below. Nights of 36°F, when frost can still settle on leaves in low, open spots, continue 14 days longer, to about June 15, and return around September 19. Severe cold of 16°F or below comes every winter, usually between November 4 and April 3.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | May 31 | Jun 5 | Jun 8 | Jun 12 | Jun 15 | Jun 18 | Jun 21 | Jun 25 | Jul 1 |
| 32°F | May 16 | May 22 | May 26 | May 29 | Jun 1 | Jun 4 | Jun 8 | Jun 13 | Jun 19 |
| 28°F | Apr 30 | May 4 | May 9 | May 12 | May 17 | May 21 | May 26 | May 31 | Jun 8 |
| 24°F | Apr 15 | Apr 21 | Apr 25 | Apr 28 | Apr 30 | May 3 | May 6 | May 11 | May 19 |
| 20°F | Apr 1 | Apr 6 | Apr 10 | Apr 14 | Apr 18 | Apr 21 | Apr 24 | Apr 28 | May 2 |
| 16°F | Mar 10 | Mar 18 | Mar 25 | Mar 30 | Apr 3 | Apr 6 | Apr 11 | Apr 16 | Apr 22 |
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Sep 5 | Sep 9 | Sep 13 | Sep 16 | Sep 19 | Sep 21 | Sep 24 | Sep 26 | Sep 29 |
| 32°F | Sep 13 | Sep 19 | Sep 22 | Sep 25 | Sep 27 | Sep 30 | Oct 2 | Oct 5 | Oct 8 |
| 28°F | Sep 24 | Sep 28 | Oct 1 | Oct 3 | Oct 6 | Oct 9 | Oct 12 | Oct 15 | Oct 20 |
| 24°F | Oct 1 | Oct 5 | Oct 9 | Oct 12 | Oct 15 | Oct 18 | Oct 21 | Oct 25 | Oct 31 |
| 20°F | Oct 10 | Oct 15 | Oct 18 | Oct 22 | Oct 25 | Oct 28 | Nov 1 | Nov 4 | Nov 9 |
| 16°F | Oct 18 | Oct 24 | Oct 29 | Nov 1 | Nov 4 | Nov 7 | Nov 11 | Nov 16 | Nov 20 |
Freeze probabilities 1991–2020 at Fort Lewis, CO, from NOAA NCEI U.S. Climate Normals. Where a temperature is reached in fewer than 99.5% of years, the dates describe only the years that reach it. Not a forecast.
Frost risk on any date in 81326 →Compare Hesperus with another place →
Weather by month in Hesperus
July is the warmest month at Fort Lewis, CO, averaging 80°F by day and 51°F at night; January is the coldest at 36°F and 12°F. A freezing night is all but certain in every month from October to May (a 90% chance or more). From July to August the chance of a 32°F night stays under 10% each month. In spring, June still brings one in 50% of years.
Warmth for growing adds up to 1,577 growing degree days a year (base 50°F), fewer than at 75% of the 110 Colorado stations. 25% of them (398) have built up by the end of June, and July adds the most, 487.
| Month | High °F | Low °F | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|
| Jan | 36 | 12 | 100% | 31 | 0 |
| Feb | 40 | 17 | 100% | 28 | 0 |
| Mar | 48 | 23 | 100% | 29 | 0 |
| Apr | 56 | 29 | 100% | 24 | 10 |
| May | 66 | 36 | 99% | 13 | 91 |
| Jun | 76 | 43 | 50% | 2 | 296 |
| Jul | 80 | 51 | 2% | <1 | 487 |
| Aug | 78 | 50 | 0% | <1 | 436 |
| Sep | 71 | 43 | 63% | 2 | 224 |
| Oct | 60 | 32 | 100% | 17 | 32 |
| Nov | 46 | 22 | 100% | 28 | 0 |
| Dec | 36 | 14 | 100% | 31 | 0 |
Monthly normals 1991–2020 at Fort Lewis, CO (7,614 ft), NOAA NCEI. "32°F night": chance of at least one in the month. GDD: growing degree days, base 50°F.
Compared with the next station
The nearest other station, Mancos 1SW, CO, 17 miles northwest of Hesperus and 717 feet lower, has a last frost 3 days later (June 4), a first frost 3 days earlier (September 24), a season 5 days shorter.
When it snows in Hesperus, Colorado
The first measurable snow (0.1 inch or more) in Hesperus usually arrives around November 11, and the last of the season around April 20. Those are the middle dates across the winters of 1991–2020 at Hesperus 13.3 SSW, CO, 1.6 miles away: half of years saw snow earlier, half later. Every one of those winters saw snow. The last 32°F night of spring typically comes 42 days after the last snow.
Planting calendar for 81326
| When | What to do |
|---|---|
| March 23 – April 6 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| April 6 – April 20 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| May 4 – May 18 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| June 1 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by July 5 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by September 13 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| September 27 onward | Plant garlic, mulch beds, lift tender bulbsGarlic wants a cold spell; bare soil loses structure over winter. |
The weeks before and after the 50% dates are general rules of thumb, not NOAA figures; a seed packet gives the timing for each variety.
Where these figures come from
ZIP 81326 is 9 miles from Fort Lewis, CO, which stands at 7,614 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 81326 in zone 6a, the band where the coldest night of the year averaged -10 to -5°F (-23.3 to -20.6°C) over 1991–2020; a zone describes winter lows, not frost dates.
Hardiness zone and temperature range: USDA Plant Hardiness Zone Map 2023 (USDA-ARS, Oregon State University), ZIP-code listing, unchanged. °C converted from °F by this site.
Thirty-year averages, not a forecast: check the forecast before planting out. How stations are matched and which pages are offered to search engines: methodology.