Frost dates for 82643Midwest, WY
The average last spring frost in Midwest is May 22 and the average first fall frost is September 22, giving a typical growing season of about 121 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- May 22
- Average first fall frost
- Sep 22
- Growing season
- 121 days
Safer after Jun 6 (1-in-10 risk)
Possible by Sep 8 (1-in-10 risk)
Last frost typically in 207 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 22 · Jun 5 · Jun 23 | Aug 29 · Sep 12 · Sep 24 | 95 days | 100% |
| Frost / freeze (32°F) | May 8 · May 22 · Jun 6 | Sep 8 · Sep 22 · Oct 5 | 121 days | 100% |
| Hard freeze (28°F) | Apr 28 · May 9 · May 24 | Sep 17 · Oct 2 · Oct 17 | 143 days | 100% |
Planting calendar for Midwest
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 21 – Jun 27 |
| Tomatoes | Transplant outdoors | Jun 7 – Jun 2 |
| Peppers | Start seeds indoors | Apr 21 – May 22 |
| Peppers | Transplant outdoors | Jun 21 – Jul 22 |
| Eggplant | Start seeds indoors | May 8 – Jun 6 |
| Eggplant | Transplant outdoors | Jun 21 – Jul 22 |
| Cucumbers | Sow outdoors | Jun 21 – Jun 12 |
| Summer squash | Sow outdoors | Jun 7 – Jul 22 |
| Winter squash & pumpkins | Sow outdoors | Jun 21 – Jul 22 |
| Snap beans | Sow outdoors | Jun 7 – Jul 5 |
| Sweet corn | Sow outdoors | Jun 7 – Jun 2 |
| Watermelon & cantaloupe | Sow outdoors | Jun 21 – Jul 22 |
| Okra | Sow outdoors | Jun 14 – Jul 7 |
| Peas | Sow outdoors (spring) | Apr 21 – Jun 6 |
| Potatoes | Plant outdoors (spring) | Apr 21 – Jun 21 |
| Onions | Start seeds indoors (spring) | Mar 10 – Apr 6 |
| Onions | Transplant outdoors (spring) | May 8 – Jun 6 |
| Broccoli | Start seeds indoors (spring) | Apr 3 – May 7 |
| Broccoli | Transplant outdoors (spring) | May 8 – Jun 6 |
| Broccoli | Start seeds indoors (fall) | May 23 – Jun 2 |
| Broccoli | Transplant outdoors (fall) | Jun 22 – Jul 3 |
| Cabbage | Start seeds indoors (spring) | Mar 24 – Apr 21 |
| Cabbage | Transplant outdoors (spring) | Apr 21 – May 22 |
| Cabbage | Start seeds indoors (fall) | May 13 – Jun 12 |
| Cabbage | Transplant outdoors (fall) | Jun 12 – Jul 13 |
| Leaf lettuce | Sow outdoors (spring) | Apr 21 – Jul 7 |
| Leaf lettuce | Sow outdoors (fall) | Jun 12 – Jul 29 |
| Spinach | Sow outdoors (spring) | Apr 14 – May 28 |
| Spinach | Sow outdoors (fall) | Jun 29 – Aug 3 |
| Radishes | Sow outdoors (spring) | Apr 21 – Jun 11 |
| Radishes | Sow outdoors (fall) | Jun 12 – Aug 13 |
| Kale | Sow outdoors (spring) | May 8 – May 28 |
| Kale | Sow outdoors (fall) | Jun 5 – Jul 13 |
| Carrots | Sow outdoors (spring) | May 22 – Jul 7 |
| Carrots | Sow outdoors (fall) | May 13 – Jun 28 |
| Garlic | Plant outdoors (fall) | Sep 12 – Oct 13 |
Where these dates come from
ZIP code 82643 is matched to the NOAA station Midwest, WY, 0.3 km away, at 4,860 ft elevation (11 ft higher than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Midwest, WY (used) | 4,860 ft | May 22 | Sep 22 |
| Kaycee, WY | 4,660 ft | May 18 | Sep 25 |
| Wright 12W, WY | 5,020 ft | May 25 | Sep 23 |
| Casper Natrona Co Ap, WY | 5,338 ft | May 26 | Sep 22 |
Frost dates near Midwest
- Edgerton, WY 82635 · last May 22, first Sep 22
- Linch, WY 82640 · last May 22, first Sep 22
- Kaycee, WY 82639 · last May 18, first Sep 25
- Evansville, WY 82636 · last May 10, first Sep 29
- Casper, WY 82602 · last May 26, first Sep 22
- Natrona, WY 82646 · last May 23, first Sep 20
- Mills, WY 82644 · last May 10, first Sep 29
- Powder River, WY 82648 · last May 30, first Sep 22
Frequently asked questions
- When is the last frost in Midwest, WY?
- For ZIP code 82643, the average last spring frost (32°F) is May 22, based on NOAA 1991-2020 climate normals for the Midwest, WY weather station. There is a 1-in-10 chance of a frost after June 6.
- When is the first frost in Midwest, WY?
- The average first fall frost (32°F) is September 22. There is a 1-in-10 chance of frost by September 8, so tender plants are at risk from that point on.
- How long is the growing season in 82643?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 121 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.