Frost dates for 82441Shell, WY
The average last spring frost in Shell is May 16 and the average first fall frost is September 24, giving a typical growing season of about 130 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- May 16
- Average first fall frost
- Sep 24
- Growing season
- 130 days
Safer after Jun 3 (1-in-10 risk)
Possible by Sep 10 (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 18 · Jun 2 · Jun 20 | Aug 23 · Sep 13 · Sep 28 | 100 days | 100% |
| Frost / freeze (32°F) | May 4 · May 16 · Jun 3 | Sep 10 · Sep 24 · Oct 7 | 130 days | 100% |
| Hard freeze (28°F) | Apr 22 · May 4 · May 15 | Sep 22 · Oct 4 · Oct 17 | 152 days | 100% |
Planting calendar for Shell
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 15 – Jun 21 |
| Tomatoes | Transplant outdoors | Jun 1 – Jun 4 |
| Peppers | Start seeds indoors | Apr 15 – May 16 |
| Peppers | Transplant outdoors | Jun 15 – Jul 16 |
| Eggplant | Start seeds indoors | May 2 – May 31 |
| Eggplant | Transplant outdoors | Jun 15 – Jul 16 |
| Cucumbers | Sow outdoors | Jun 15 – Jun 14 |
| Summer squash | Sow outdoors | Jun 1 – Jul 16 |
| Winter squash & pumpkins | Sow outdoors | Jun 15 – Jul 16 |
| Snap beans | Sow outdoors | Jun 1 – Jul 7 |
| Sweet corn | Sow outdoors | Jun 1 – Jun 4 |
| Watermelon & cantaloupe | Sow outdoors | Jun 15 – Jul 16 |
| Okra | Sow outdoors | Jun 8 – Jul 1 |
| Peas | Sow outdoors (spring) | Apr 15 – May 31 |
| Potatoes | Plant outdoors (spring) | Apr 15 – Jun 15 |
| Onions | Start seeds indoors (spring) | Mar 4 – Mar 31 |
| Onions | Transplant outdoors (spring) | May 2 – May 31 |
| Broccoli | Start seeds indoors (spring) | Mar 28 – May 1 |
| Broccoli | Transplant outdoors (spring) | May 2 – May 31 |
| Broccoli | Start seeds indoors (fall) | May 25 – Jun 4 |
| Broccoli | Transplant outdoors (fall) | Jun 24 – Jul 5 |
| Cabbage | Start seeds indoors (spring) | Mar 18 – Apr 15 |
| Cabbage | Transplant outdoors (spring) | Apr 15 – May 16 |
| Cabbage | Start seeds indoors (fall) | May 15 – Jun 14 |
| Cabbage | Transplant outdoors (fall) | Jun 14 – Jul 15 |
| Leaf lettuce | Sow outdoors (spring) | Apr 15 – Jul 1 |
| Leaf lettuce | Sow outdoors (fall) | Jun 14 – Jul 31 |
| Spinach | Sow outdoors (spring) | Apr 8 – May 22 |
| Spinach | Sow outdoors (fall) | Jul 1 – Aug 5 |
| Radishes | Sow outdoors (spring) | Apr 15 – Jun 5 |
| Radishes | Sow outdoors (fall) | Jun 14 – Aug 15 |
| Kale | Sow outdoors (spring) | May 2 – May 22 |
| Kale | Sow outdoors (fall) | Jun 7 – Jul 15 |
| Carrots | Sow outdoors (spring) | May 16 – Jul 1 |
| Carrots | Sow outdoors (fall) | May 15 – Jun 30 |
| Garlic | Plant outdoors (fall) | Sep 14 – Oct 15 |
Where these dates come from
ZIP code 82441 is matched to the NOAA station Shell, WY, 7.4 km away, at 4,242 ft elevation (604 ft lower than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Shell, WY (used) | 4,242 ft | May 16 | Sep 24 |
| Greybull, WY | 3,787 ft | May 11 | Sep 23 |
| Greybull S Big Horn Ap, WY | 3,933 ft | May 4 | Oct 1 |
| Burgess Junction, WY | 8,060 ft | — | — |
Frost dates near Shell
- Greybull, WY 82426 · last May 4, first Oct 1
- Basin, WY 82410 · last Apr 28, first Oct 10
- Manderson, WY 82432 · last Apr 28, first Oct 10
- Hyattville, WY 82428 · last May 10, first Oct 1
- Otto, WY 82434 · last May 12, first Sep 28
- Emblem, WY 82422 · last May 12, first Sep 28
- Dayton, WY 82836 · last May 24, first Sep 18
- Wolf, WY 82844 · last May 21, first Sep 23
Frequently asked questions
- When is the last frost in Shell, WY?
- For ZIP code 82441, the average last spring frost (32°F) is May 16, based on NOAA 1991-2020 climate normals for the Shell, WY weather station. There is a 1-in-10 chance of a frost after June 3.
- When is the first frost in Shell, WY?
- The average first fall frost (32°F) is September 24. There is a 1-in-10 chance of frost by September 10, so tender plants are at risk from that point on.
- How long is the growing season in 82441?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 130 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.