USDA Hardiness Zone 5a
Frost Dates for 82937 — Lyman, Wyoming
NOAA 1991–2020 normals from Mountain View, WY (6,800 ft), 9 miles south.
Updated
In Lyman, the last spring frost (32°F) is around June 14 in half of years and has passed by July 1 in nine years out of ten. The first fall frost comes around September 9, as early as August 23 one year in ten, leaving a typical freeze-free season of 84 days (NOAA, Mountain View, WY).
- Last spring frost
- June 14
- First fall frost
- September 9
- Growing season
- 84 days
- Hardiness zone
- 5a
50% probability
50% probability
freeze-free, 50%
-20 to -15°F (-28.9 to -26.1°C) coldest night
- First snow
- October 11
- Last snow
- May 5
- Winters with snow
- 100%
- Snow per year
- 63.8"
median, 1991–2020
median, 1991–2020
27 of 27 observed
NOAA normal
Frost risk by date in Lyman
Half of springs at Mountain View, WY see their last 32°F night by June 14; only one in ten is past it by May 31, and one in ten still has one after July 1. Planting tender crops after June 21 leaves a 30% risk of a frost on them, after June 26 20%, and after July 1 10%. The 17 days between the even-odds date and the one-in-ten date is wider than at 73% of the 33 Wyoming 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 23 one year in ten, and holds off past September 21 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 17, 14 days before the 32°F one. The freeze-free season lasts 84 days in a typical year, shorter than at 88% of the 33 Wyoming stations; it reaches 104 days one year in ten and falls short of 59 one year in ten. On average 206 nights a year drop to 32°F or below. Severe cold of 16°F or below comes every winter, usually between October 25 and April 18.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | too rare for a date | ||||||||
| 32°F | May 31 | Jun 4 | Jun 8 | Jun 11 | Jun 14 | Jun 17 | Jun 21 | Jun 26 | Jul 1 |
| 28°F | May 15 | May 19 | May 23 | May 27 | May 30 | Jun 2 | Jun 5 | Jun 10 | Jun 17 |
| 24°F | Apr 29 | May 3 | May 7 | May 10 | May 14 | May 17 | May 21 | May 26 | Jun 1 |
| 20°F | Apr 14 | Apr 20 | Apr 24 | Apr 27 | Apr 30 | May 3 | May 6 | May 11 | May 16 |
| 16°F | Mar 31 | Apr 6 | Apr 10 | Apr 14 | Apr 18 | Apr 22 | Apr 26 | Apr 30 | May 5 |
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | too rare for a date | ||||||||
| 32°F | Aug 23 | Aug 30 | Sep 3 | Sep 6 | Sep 9 | Sep 11 | Sep 14 | Sep 18 | Sep 21 |
| 28°F | Sep 5 | Sep 10 | Sep 14 | Sep 17 | Sep 20 | Sep 23 | Sep 25 | Sep 28 | Oct 1 |
| 24°F | Sep 16 | Sep 21 | Sep 24 | Sep 27 | Sep 30 | Oct 2 | Oct 5 | Oct 9 | Oct 16 |
| 20°F | Sep 26 | Sep 30 | Oct 4 | Oct 8 | Oct 12 | Oct 16 | Oct 19 | Oct 24 | Oct 29 |
| 16°F | Oct 6 | Oct 13 | Oct 18 | Oct 22 | Oct 25 | Oct 28 | Oct 31 | Nov 3 | Nov 7 |
Freeze probabilities 1991–2020 at Mountain View, WY, 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 82937 →Compare Lyman with another place →
Weather by month in Lyman
July is the warmest month at Mountain View, WY, averaging 80°F by day and 47°F at night; December is the coldest at 31°F and 11°F. A freezing night is all but certain in every month from September to May (a 90% chance or more). No month is safe from a 32°F night: even the warmest has at least a 10% chance. In spring, June still brings one in 86% of years and July still brings one in 11% of years.
Warmth for growing adds up to 1,223 growing degree days a year (base 50°F), fewer than at 94% of the 33 Wyoming stations. 23% of them (280) have built up by the end of June, and July adds the most, 410. Precipitation totals 11.2 inches a year, most in May (1.4") and least in January (0.6"); May to September bring 49% of it.
| Month | High °F | Low °F | Precip. in | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|---|
| Jan | 32 | 11 | 0.6 | 100% | 30 | 0 |
| Feb | 34 | 11 | 0.6 | 100% | 28 | 0 |
| Mar | 44 | 20 | 0.8 | 100% | 29 | 0 |
| Apr | 52 | 25 | 1.1 | 100% | 23 | 6 |
| May | 63 | 33 | 1.4 | 100% | 11 | 63 |
| Jun | 73 | 40 | 0.9 | 86% | 2 | 211 |
| Jul | 80 | 47 | 1.1 | 11% | <1 | 410 |
| Aug | 78 | 45 | 0.8 | 23% | <1 | 363 |
| Sep | 70 | 37 | 1.3 | 100% | 5 | 151 |
| Oct | 57 | 28 | 1.0 | 100% | 20 | 21 |
| Nov | 41 | 17 | 0.8 | 100% | 28 | 0 |
| Dec | 31 | 11 | 0.8 | 100% | 30 | 0 |
Monthly normals 1991–2020 at Mountain View, WY (6,800 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, Evanston 1 E, WY, 32 miles west of Lyman, has a last frost 2 days earlier (June 12), a first frost 3 days later (September 12), a season 6 days longer.
When it snows in Lyman, Wyoming
The first measurable snow (0.1 inch or more) in Lyman usually arrives around October 11, and the last of the season around May 5. Those are the middle dates across the winters of 1991–2020 at Mountain View, WY, 9.4 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 82937
| When | What to do |
|---|---|
| April 5 – April 19 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| April 19 – May 3 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| May 17 – May 31 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| June 14 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 82937 is 9 miles from Mountain View, WY, which stands at 6,800 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 82937 in zone 5a, the band where the coldest night of the year averaged -20 to -15°F (-28.9 to -26.1°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.