Frost dates for 82420Cowley, WY
The average last spring frost in Cowley is May 9 and the average first fall frost is September 29, giving a typical growing season of about 142 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- May 9
- Average first fall frost
- Sep 29
- Growing season
- 142 days
Safer after May 25 (1-in-10 risk)
Possible by Sep 16 (1-in-10 risk)
Last frost typically in 194 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 7 · May 22 · Jun 6 | Sep 7 · Sep 19 · Oct 2 | 120 days | 100% |
| Frost / freeze (32°F) | Apr 27 · May 9 · May 25 | Sep 16 · Sep 29 · Oct 11 | 142 days | 100% |
| Hard freeze (28°F) | Apr 15 · Apr 29 · May 12 | Sep 25 · Oct 9 · Oct 23 | 162 days | 100% |
Planting calendar for Cowley
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 8 – Jun 14 |
| Tomatoes | Transplant outdoors | May 25 – Jun 9 |
| Peppers | Start seeds indoors | Apr 8 – May 9 |
| Peppers | Transplant outdoors | Jun 8 – Jul 9 |
| Eggplant | Start seeds indoors | Apr 25 – May 24 |
| Eggplant | Transplant outdoors | Jun 8 – Jul 9 |
| Cucumbers | Sow outdoors | Jun 8 – Jun 19 |
| Summer squash | Sow outdoors | May 25 – Jul 9 |
| Winter squash & pumpkins | Sow outdoors | Jun 8 – Jul 9 |
| Snap beans | Sow outdoors | May 25 – Jul 12 |
| Sweet corn | Sow outdoors | May 25 – Jun 9 |
| Watermelon & cantaloupe | Sow outdoors | Jun 8 – Jul 9 |
| Okra | Sow outdoors | Jun 1 – Jun 24 |
| Peas | Sow outdoors (spring) | Apr 8 – May 24 |
| Potatoes | Plant outdoors (spring) | Apr 8 – Jun 8 |
| Onions | Start seeds indoors (spring) | Feb 25 – Mar 24 |
| Onions | Transplant outdoors (spring) | Apr 25 – May 24 |
| Broccoli | Start seeds indoors (spring) | Mar 21 – Apr 24 |
| Broccoli | Transplant outdoors (spring) | Apr 25 – May 24 |
| Broccoli | Start seeds indoors (fall) | May 30 – Jun 9 |
| Broccoli | Transplant outdoors (fall) | Jun 29 – Jul 10 |
| Cabbage | Start seeds indoors (spring) | Mar 11 – Apr 8 |
| Cabbage | Transplant outdoors (spring) | Apr 8 – May 9 |
| Cabbage | Start seeds indoors (fall) | May 20 – Jun 19 |
| Cabbage | Transplant outdoors (fall) | Jun 19 – Jul 20 |
| Leaf lettuce | Sow outdoors (spring) | Apr 8 – Jun 24 |
| Leaf lettuce | Sow outdoors (fall) | Jun 19 – Aug 5 |
| Spinach | Sow outdoors (spring) | Apr 1 – May 15 |
| Spinach | Sow outdoors (fall) | Jul 6 – Aug 10 |
| Radishes | Sow outdoors (spring) | Apr 8 – May 29 |
| Radishes | Sow outdoors (fall) | Jun 19 – Aug 20 |
| Kale | Sow outdoors (spring) | Apr 25 – May 15 |
| Kale | Sow outdoors (fall) | Jun 12 – Jul 20 |
| Carrots | Sow outdoors (spring) | May 9 – Jun 24 |
| Carrots | Sow outdoors (fall) | May 20 – Jul 5 |
| Garlic | Plant outdoors (fall) | Sep 19 – Oct 20 |
Where these dates come from
ZIP code 82420 is matched to the NOAA station Lovell, WY, 7 km away, at 3,847 ft elevation (156 ft lower than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Lovell, WY (used) | 3,847 ft | May 9 | Sep 29 |
| Deaver, WY | 4,105 ft | May 6 | Oct 1 |
| Powell Fld Stn, WY | 4,372 ft | May 19 | Sep 20 |
| Emblem, WY | 4,448 ft | May 12 | Sep 28 |
Frost dates near Cowley
- Lovell, WY 82431 · last May 9, first Sep 29
- Deaver, WY 82421 · last May 6, first Oct 1
- Byron, WY 82412 · last May 6, first Oct 1
- Frannie, WY 82423 · last May 6, first Oct 1
- Powell, WY 82435 · last May 19, first Sep 20
- Ralston, WY 82440 · last May 15, first Sep 25
- Emblem, WY 82422 · last May 12, first Sep 28
- Burlington, WY 82411 · last May 12, first Sep 28
Frequently asked questions
- When is the last frost in Cowley, WY?
- For ZIP code 82420, the average last spring frost (32°F) is May 9, based on NOAA 1991-2020 climate normals for the Lovell, WY weather station. There is a 1-in-10 chance of a frost after May 25.
- When is the first frost in Cowley, WY?
- The average first fall frost (32°F) is September 29. There is a 1-in-10 chance of frost by September 16, so tender plants are at risk from that point on.
- How long is the growing season in 82420?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 142 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.