USDA Hardiness Zone 6a
Frost Dates for 81432 — Ridgway, Colorado
NOAA 1991–2020 normals from Ridgway, CO (7,049 ft), 2 miles northeast.
Updated
In Ridgway, the last spring frost (32°F) is around June 11 in half of years and has passed by June 30 in nine years out of ten. The first fall frost comes around September 13, as early as September 1 one year in ten, leaving a typical freeze-free season of 92 days (NOAA, Ridgway, CO).
- Last spring frost
- June 11
- First fall frost
- September 13
- Growing season
- 92 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
- October 24
- Last snow
- April 21
- Winters with snow
- 100%
- Snow per year
- 81"
median, 1991–2020
median, 1991–2020
26 of 26 observed
NOAA normal
Frost risk by date in Ridgway
Half of springs at Ridgway, CO see their last 32°F night by June 11; only one in ten is past it by May 27, and one in ten still has one after June 30. Planting tender crops after June 18 leaves a 30% risk of a frost on them, after June 23 20%, and after June 30 10%. The 19 days between the even-odds date and the one-in-ten date is wider than at 95% of the 110 Colorado stations behind this site's ZIP pages.
In fall the first 32°F night comes by September 13 in half of years, as early as September 1 one year in ten, and holds off past September 25 one year in ten. A hard freeze of 28°F follows 10 days later, around September 23; in spring the one-in-ten date for 28°F is June 14, 16 days before the 32°F one. The freeze-free season lasts 92 days in a typical year, shorter than at 88% of the 110 Colorado stations; it reaches 112 days one year in ten and falls short of 71 one year in ten. On average 223 nights a year drop to 32°F or below. Severe cold of 16°F or below comes every winter, usually between October 23 and April 9.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | too rare for a date | ||||||||
| 32°F | May 27 | Jun 1 | Jun 5 | Jun 8 | Jun 11 | Jun 14 | Jun 18 | Jun 23 | Jun 30 |
| 28°F | May 5 | May 14 | May 19 | May 22 | May 26 | May 31 | Jun 3 | Jun 7 | Jun 14 |
| 24°F | Apr 24 | Apr 28 | May 1 | May 4 | May 8 | May 13 | May 17 | May 23 | May 31 |
| 20°F | Apr 7 | Apr 12 | Apr 16 | Apr 20 | Apr 23 | Apr 26 | Apr 30 | May 2 | May 7 |
| 16°F | Mar 22 | Mar 31 | Apr 3 | Apr 6 | Apr 9 | Apr 11 | Apr 15 | Apr 19 | Apr 25 |
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | too rare for a date | ||||||||
| 32°F | Sep 1 | Sep 5 | Sep 8 | Sep 10 | Sep 13 | Sep 15 | Sep 18 | Sep 22 | Sep 25 |
| 28°F | Sep 10 | Sep 14 | Sep 17 | Sep 20 | Sep 23 | Sep 25 | Sep 28 | Oct 1 | Oct 4 |
| 24°F | Sep 19 | Sep 24 | Sep 27 | Sep 30 | Oct 2 | Oct 4 | Oct 6 | Oct 9 | Oct 14 |
| 20°F | Sep 29 | Oct 3 | Oct 6 | Oct 9 | Oct 13 | Oct 15 | Oct 18 | Oct 21 | Oct 26 |
| 16°F | Oct 9 | Oct 14 | Oct 18 | Oct 20 | Oct 23 | Oct 26 | Oct 29 | Nov 2 | Nov 6 |
Freeze probabilities 1991–2020 at Ridgway, 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 81432 →Compare Ridgway with another place →
Weather by month in Ridgway
July is the warmest month at Ridgway, CO, averaging 85°F by day and 46°F at night; January is the coldest at 40°F and 7°F. A freezing night is all but certain in every month from September 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 80% of years.
Warmth for growing adds up to 1,584 growing degree days a year (base 50°F), fewer than at 74% of the 110 Colorado stations. 28% of them (445) have built up by the end of June, and July adds the most, 491. Precipitation totals 16.1 inches a year, most in August (2.0") and least in June (0.8"); May to September bring 48% of it.
| Month | High °F | Low °F | Precip. in | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|---|
| Jan | 40 | 7 | 1.0 | 100% | 31 | 0 |
| Feb | 44 | 12 | 0.9 | 100% | 28 | 0 |
| Mar | 53 | 20 | 1.3 | 100% | 30 | 1 |
| Apr | 59 | 26 | 1.4 | 100% | 24 | 13 |
| May | 70 | 34 | 1.5 | 100% | 14 | 116 |
| Jun | 81 | 39 | 0.8 | 80% | 3 | 315 |
| Jul | 85 | 46 | 1.9 | 10% | <1 | 491 |
| Aug | 82 | 45 | 2.0 | 9% | <1 | 418 |
| Sep | 76 | 36 | 1.6 | 97% | 8 | 202 |
| Oct | 64 | 26 | 1.4 | 100% | 25 | 27 |
| Nov | 51 | 16 | 1.2 | 100% | 29 | 1 |
| Dec | 40 | 8 | 1.1 | 100% | 31 | 0 |
Monthly normals 1991–2020 at Ridgway, CO (7,049 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, Placerville, CO, 17 miles southwest of Ridgway and 334 feet higher, has a last frost 16 days earlier (May 26), a first frost 16 days later (September 29), a season 33 days longer.
When it snows in Ridgway, Colorado
The first measurable snow (0.1 inch or more) in Ridgway usually arrives around October 24, and the last of the season around April 21. Those are the middle dates across the winters of 1991–2020 at Ridgway, CO, 1.5 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 51 days after the last snow.
Planting calendar for 81432
| 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 21 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by August 30 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| September 13 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 81432 is 2 miles from Ridgway, CO, which stands at 7,049 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 81432 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.