USDA Hardiness Zone 5b
Frost Dates for 81223 — Cotopaxi, Colorado
NOAA 1991–2020 normals from Westcliffe, CO (7,873 ft), 16 miles south.
Updated
In Cotopaxi, the last spring frost (32°F) is around June 11 in half of years and has passed by June 28 in nine years out of ten. The first fall frost comes around September 9, as early as August 28 one year in ten, leaving a typical freeze-free season of 89 days (NOAA, Westcliffe, CO).
- Last spring frost
- June 11
- First fall frost
- September 9
- Growing season
- 89 days
- Hardiness zone
- 5b
50% probability
50% probability
freeze-free, 50%
-15 to -10°F (-26.1 to -23.3°C) coldest night
- First snow
- October 21
- Last snow
- May 2
- Winters with snow
- 100%
- Snow per year
- —
median, 1991–2020
median, 1991–2020
16 of 16 observed
NOAA normal
Frost risk by date in Cotopaxi
Half of springs at Westcliffe, CO see their last 32°F night by June 11; only one in ten is past it by May 29, and one in ten still has one after June 28. Planting tender crops after June 18 leaves a 30% risk of a frost on them, after June 23 20%, and after June 28 10%. The 17 days between the even-odds date and the one-in-ten date is wider than at 85% of the 110 Colorado stations behind this site's ZIP pages.
In fall the first 32°F night comes by September 9 in half of years, as early as August 28 one year in ten, and holds off past September 23 one year in ten. A hard freeze of 28°F follows 11 days later, around September 20; in spring the one-in-ten date for 28°F is June 13, 15 days before the 32°F one. The freeze-free season lasts 89 days in a typical year, shorter than at 91% of the 110 Colorado stations; it reaches 108 days one year in ten and falls short of 68 one year in ten. On average 213 nights a year drop to 32°F or below. Severe cold of 16°F or below comes every winter, usually between October 13 and April 24.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | too rare for a date | ||||||||
| 32°F | May 29 | Jun 2 | Jun 4 | Jun 7 | Jun 11 | Jun 14 | Jun 18 | Jun 23 | Jun 28 |
| 28°F | May 16 | May 19 | May 22 | May 24 | May 28 | May 31 | Jun 3 | Jun 7 | Jun 13 |
| 24°F | May 3 | May 6 | May 9 | May 11 | May 14 | May 16 | May 19 | May 23 | May 30 |
| 20°F | Apr 20 | Apr 25 | Apr 28 | May 1 | May 3 | May 6 | May 8 | May 10 | May 15 |
| 16°F | Apr 8 | Apr 14 | Apr 18 | Apr 20 | Apr 24 | Apr 26 | Apr 30 | May 3 | May 7 |
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | too rare for a date | ||||||||
| 32°F | Aug 28 | Sep 1 | Sep 4 | Sep 6 | Sep 9 | Sep 11 | Sep 14 | Sep 18 | Sep 23 |
| 28°F | Sep 6 | Sep 10 | Sep 13 | Sep 17 | Sep 20 | Sep 23 | Sep 26 | Sep 29 | Oct 2 |
| 24°F | Sep 16 | Sep 20 | Sep 24 | Sep 26 | Sep 29 | Oct 1 | Oct 3 | Oct 6 | Oct 10 |
| 20°F | Sep 24 | Sep 29 | Oct 1 | Oct 3 | Oct 6 | Oct 8 | Oct 11 | Oct 14 | Oct 19 |
| 16°F | Sep 30 | Oct 4 | Oct 7 | Oct 11 | Oct 13 | Oct 16 | Oct 19 | Oct 22 | Oct 28 |
Freeze probabilities 1991–2020 at Westcliffe, 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 81223 →Compare Cotopaxi with another place →
Weather by month in Cotopaxi
July is the warmest month at Westcliffe, CO, averaging 81°F by day and 45°F at night; December is the coldest at 40°F and 8°F. A freezing night is all but certain in every month from September to May (a 90% chance or more). July is the only month with under a 10% chance of a 32°F night. In spring, June still brings one in 82% of years.
Warmth for growing adds up to 1,279 growing degree days a year (base 50°F), fewer than at 84% of the 110 Colorado stations. 28% of them (354) have built up by the end of June, and July adds the most, 395. Precipitation totals 13.8 inches a year, most in July (2.7") and least in January (0.5"); May to September bring 57% of it.
| Month | High °F | Low °F | Precip. in | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|---|
| Jan | 40 | 8 | 0.5 | 100% | 30 | 0 |
| Feb | 42 | 12 | 0.6 | 100% | 27 | 0 |
| Mar | 50 | 20 | 1.1 | 100% | 28 | 1 |
| Apr | 56 | 26 | 1.6 | 100% | 23 | 11 |
| May | 66 | 33 | 1.4 | 100% | 13 | 76 |
| Jun | 77 | 41 | 0.8 | 82% | 2 | 266 |
| Jul | 81 | 45 | 2.7 | 6% | <1 | 395 |
| Aug | 78 | 44 | 2.0 | 16% | <1 | 343 |
| Sep | 72 | 37 | 0.9 | 97% | 8 | 163 |
| Oct | 61 | 26 | 1.0 | 100% | 23 | 22 |
| Nov | 49 | 17 | 0.7 | 100% | 28 | 2 |
| Dec | 40 | 8 | 0.5 | 100% | 30 | 0 |
Monthly normals 1991–2020 at Westcliffe, CO (7,873 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, Canon City, CO, 18 miles northeast of Cotopaxi and 2,495 feet lower, has a last frost 38 days earlier (May 4), a first frost 28 days later (October 7), a season 64 days longer.
When it snows in Cotopaxi, Colorado
The first measurable snow (0.1 inch or more) in Cotopaxi usually arrives around October 21, and the last of the season around May 2. Those are the middle dates across the winters of 1991–2020 at Cotopaxi 4.8 SSE, CO, 6.8 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 40 days after the last snow.
Planting calendar for 81223
| When | What to do |
|---|---|
| April 2 – April 16 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| April 16 – April 30 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| May 14 – May 28 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| June 11 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by June 17 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by August 26 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| September 9 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 81223 is 16 miles from Westcliffe, CO, which stands at 7,873 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 1 other ZIP code shares the station; its figures are presented in full for 81252 (Westcliffe). The 2023 USDA Plant Hardiness Zone Map lists ZIP 81223 in zone 5b, the band where the coldest night of the year averaged -15 to -10°F (-26.1 to -23.3°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.