Frost dates for 82646Natrona, WY
The average last spring frost in Natrona is May 23 and the average first fall frost is September 20, giving a typical growing season of about 121 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- May 23
- Average first fall frost
- Sep 20
- Growing season
- 121 days
Safer after Jun 5 (1-in-10 risk)
Possible by Sep 7 (1-in-10 risk)
Last frost typically in 201 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 23 · Jun 5 · Jun 23 | Aug 31 · Sep 10 · Sep 21 | 97 days | 100% |
| Frost / freeze (32°F) | May 9 · May 23 · Jun 5 | Sep 7 · Sep 20 · Oct 4 | 121 days | 100% |
| Hard freeze (28°F) | Apr 28 · May 10 · May 23 | Sep 17 · Oct 1 · Oct 17 | 143 days | 100% |
Planting calendar for Natrona
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 22 – Jun 28 |
| Tomatoes | Transplant outdoors | Jun 8 – May 31 |
| Peppers | Start seeds indoors | Apr 22 – May 23 |
| Peppers | Transplant outdoors | Jun 22 – Jul 23 |
| Eggplant | Start seeds indoors | May 9 – Jun 7 |
| Eggplant | Transplant outdoors | Jun 22 – Jul 23 |
| Cucumbers | Sow outdoors | Jun 22 – Jun 10 |
| Summer squash | Sow outdoors | Jun 8 – Jul 23 |
| Winter squash & pumpkins | Sow outdoors | Jun 22 – Jul 23 |
| Snap beans | Sow outdoors | Jun 8 – Jul 3 |
| Sweet corn | Sow outdoors | Jun 8 – May 31 |
| Watermelon & cantaloupe | Sow outdoors | Jun 22 – Jul 23 |
| Okra | Sow outdoors | Jun 15 – Jul 8 |
| Peas | Sow outdoors (spring) | Apr 22 – Jun 7 |
| Potatoes | Plant outdoors (spring) | Apr 22 – Jun 22 |
| Onions | Start seeds indoors (spring) | Mar 11 – Apr 7 |
| Onions | Transplant outdoors (spring) | May 9 – Jun 7 |
| Broccoli | Start seeds indoors (spring) | Apr 4 – May 8 |
| Broccoli | Transplant outdoors (spring) | May 9 – Jun 7 |
| Broccoli | Start seeds indoors (fall) | May 21 – May 31 |
| Broccoli | Transplant outdoors (fall) | Jun 20 – Jul 1 |
| Cabbage | Start seeds indoors (spring) | Mar 25 – Apr 22 |
| Cabbage | Transplant outdoors (spring) | Apr 22 – May 23 |
| Cabbage | Start seeds indoors (fall) | May 11 – Jun 10 |
| Cabbage | Transplant outdoors (fall) | Jun 10 – Jul 11 |
| Leaf lettuce | Sow outdoors (spring) | Apr 22 – Jul 8 |
| Leaf lettuce | Sow outdoors (fall) | Jun 10 – Jul 27 |
| Spinach | Sow outdoors (spring) | Apr 15 – May 29 |
| Spinach | Sow outdoors (fall) | Jun 27 – Aug 1 |
| Radishes | Sow outdoors (spring) | Apr 22 – Jun 12 |
| Radishes | Sow outdoors (fall) | Jun 10 – Aug 11 |
| Kale | Sow outdoors (spring) | May 9 – May 29 |
| Kale | Sow outdoors (fall) | Jun 3 – Jul 11 |
| Carrots | Sow outdoors (spring) | May 23 – Jul 8 |
| Carrots | Sow outdoors (fall) | May 11 – Jun 26 |
| Garlic | Plant outdoors (fall) | Sep 10 – Oct 11 |
Where these dates come from
ZIP code 82646 is matched to the NOAA station Powder River #2, WY, 14.6 km away, at 5,700 ft elevation (90 ft higher than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Powder River #2, WY (used) | 5,700 ft | May 23 | Sep 20 |
| Powder Rvr (School), WY | 5,722 ft | May 30 | Sep 22 |
| Casper Natrona Co Ap, WY | 5,338 ft | May 26 | Sep 22 |
| Casper Wwtp, WY | 5,097 ft | May 10 | Sep 29 |
Frost dates near Natrona
- Powder River, WY 82648 · last May 30, first Sep 22
- Casper, WY 82602 · last May 26, first Sep 22
- Arminto, WY 82630 · last May 30, first Sep 22
- Mills, WY 82644 · last May 10, first Sep 29
- Hiland, WY 82638 · last May 30, first Sep 22
- Evansville, WY 82636 · last May 10, first Sep 29
- Alcova, WY 82620 · last May 9, first Oct 7
- Midwest, WY 82643 · last May 22, first Sep 22
Frequently asked questions
- When is the last frost in Natrona, WY?
- For ZIP code 82646, the average last spring frost (32°F) is May 23, based on NOAA 1991-2020 climate normals for the Powder River #2, WY weather station. There is a 1-in-10 chance of a frost after June 5.
- When is the first frost in Natrona, WY?
- The average first fall frost (32°F) is September 20. 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 82646?
- 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.