Frost dates for 82721Moorcroft, WY
The average last spring frost in Moorcroft is May 21 and the average first fall frost is September 25, giving a typical growing season of about 124 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- May 21
- Average first fall frost
- Sep 25
- Growing season
- 124 days
Safer after Jun 5 (1-in-10 risk)
Possible by Sep 7 (1-in-10 risk)
Last frost typically in 200 days
Frost risk by date
NOAA reports frost dates as probabilities. The middle date is the average (a 50% chance). For spring, the 10% date is a safer planting date: frost after it happens in about 1 year in 10. Light frost (36°F) can damage tender plants; a hard freeze (28°F) kills most annuals.
| Temperature | Last spring: 90% / 50% / 10% chance | First fall: 10% / 50% / 90% chance | Growing season (50%) | Years with at least one |
|---|---|---|---|---|
| Light frost (36°F) | May 20 · Jun 1 · Jun 24 | Aug 29 · Sep 16 · Sep 29 | 101 days | 100% |
| Frost / freeze (32°F) | May 9 · May 21 · Jun 5 | Sep 7 · Sep 25 · Oct 8 | 124 days | 100% |
| Hard freeze (28°F) | Apr 27 · May 9 · May 23 | Sep 18 · Oct 4 · Oct 19 | 145 days | 100% |
Planting calendar for Moorcroft
Planting windows from the University of Maryland Extension calendar, shifted to your average frost dates. Use them as a starting point and adjust for seed packet instructions and local conditions.
| Crop | Task | Window |
|---|---|---|
| Tomatoes | Start seeds indoors | Apr 20 – Jun 26 |
| Tomatoes | Transplant outdoors | Jun 6 – Jun 5 |
| Peppers | Start seeds indoors | Apr 20 – May 21 |
| Peppers | Transplant outdoors | Jun 20 – Jul 21 |
| Eggplant | Start seeds indoors | May 7 – Jun 5 |
| Eggplant | Transplant outdoors | Jun 20 – Jul 21 |
| Cucumbers | Sow outdoors | Jun 20 – Jun 15 |
| Summer squash | Sow outdoors | Jun 6 – Jul 21 |
| Winter squash & pumpkins | Sow outdoors | Jun 20 – Jul 21 |
| Snap beans | Sow outdoors | Jun 6 – Jul 8 |
| Sweet corn | Sow outdoors | Jun 6 – Jun 5 |
| Watermelon & cantaloupe | Sow outdoors | Jun 20 – Jul 21 |
| Okra | Sow outdoors | Jun 13 – Jul 6 |
| Peas | Sow outdoors (spring) | Apr 20 – Jun 5 |
| Potatoes | Plant outdoors (spring) | Apr 20 – Jun 20 |
| Onions | Start seeds indoors (spring) | Mar 9 – Apr 5 |
| Onions | Transplant outdoors (spring) | May 7 – Jun 5 |
| Broccoli | Start seeds indoors (spring) | Apr 2 – May 6 |
| Broccoli | Transplant outdoors (spring) | May 7 – Jun 5 |
| Broccoli | Start seeds indoors (fall) | May 26 – Jun 5 |
| Broccoli | Transplant outdoors (fall) | Jun 25 – Jul 6 |
| Cabbage | Start seeds indoors (spring) | Mar 23 – Apr 20 |
| Cabbage | Transplant outdoors (spring) | Apr 20 – May 21 |
| Cabbage | Start seeds indoors (fall) | May 16 – Jun 15 |
| Cabbage | Transplant outdoors (fall) | Jun 15 – Jul 16 |
| Leaf lettuce | Sow outdoors (spring) | Apr 20 – Jul 6 |
| Leaf lettuce | Sow outdoors (fall) | Jun 15 – Aug 1 |
| Spinach | Sow outdoors (spring) | Apr 13 – May 27 |
| Spinach | Sow outdoors (fall) | Jul 2 – Aug 6 |
| Radishes | Sow outdoors (spring) | Apr 20 – Jun 10 |
| Radishes | Sow outdoors (fall) | Jun 15 – Aug 16 |
| Kale | Sow outdoors (spring) | May 7 – May 27 |
| Kale | Sow outdoors (fall) | Jun 8 – Jul 16 |
| Carrots | Sow outdoors (spring) | May 21 – Jul 6 |
| Carrots | Sow outdoors (fall) | May 16 – Jul 1 |
| Garlic | Plant outdoors (fall) | Sep 15 – Oct 16 |
Where these dates come from
ZIP code 82721 is matched to the NOAA station Sundance, WY, 38.3 km away, at 4,695 ft elevation (148 ft higher than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Sundance, WY (used) | 4,695 ft | May 21 | Sep 25 |
| Devils Twr #2, WY | 3,862 ft | May 23 | Sep 20 |
| Moorcroft 3S, WY | 4,325 ft | May 22 | Sep 28 |
| Sundance 8 Nnw, WY | 5,792 ft | May 23 | Sep 24 |
Frost dates near Moorcroft
- Devils Tower, WY 82714 · last May 23, first Sep 20
- Rozet, WY 82727 · last May 22, first Sep 25
- Sundance, WY 82729 · last May 21, first Sep 25
- Hulett, WY 82720 · last May 17, first Sep 23
- Upton, WY 82730 · last May 20, first Sep 23
- Alva, WY 82711 · last May 17, first Sep 23
- Gillette, WY 82717 · last May 15, first Oct 1
- Osage, WY 82723 · last May 20, first Sep 23
Frequently asked questions
- When is the last frost in Moorcroft, WY?
- For ZIP code 82721, the average last spring frost (32°F) is May 21, based on NOAA 1991-2020 climate normals for the Sundance, WY weather station. There is a 1-in-10 chance of a frost after June 5.
- When is the first frost in Moorcroft, WY?
- The average first fall frost (32°F) is September 25. There is a 1-in-10 chance of frost by September 7, so tender plants are at risk from that point on.
- How long is the growing season in 82721?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 124 days long.
- Are these frost dates a forecast?
- No. They are 30-year averages and probabilities from NOAA weather station records. Use them to plan, then watch your local forecast before planting tender crops or leaving them uncovered.