Frost dates for 82833Big Horn, WY
The average last spring frost in Big Horn is May 17 and the average first fall frost is September 28, giving a typical growing season of about 132 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- May 17
- Average first fall frost
- Sep 28
- Growing season
- 132 days
Safer after May 31 (1-in-10 risk)
Possible by Sep 13 (1-in-10 risk)
Last frost typically in 195 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 · May 31 · Jun 16 | Sep 3 · Sep 17 · Sep 29 | 108 days | 100% |
| Frost / freeze (32°F) | May 2 · May 17 · May 31 | Sep 13 · Sep 28 · Oct 10 | 132 days | 100% |
| Hard freeze (28°F) | Apr 20 · May 2 · May 17 | Sep 21 · Oct 5 · Oct 20 | 155 days | 100% |
Planting calendar for Big Horn
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 16 – Jun 22 |
| Tomatoes | Transplant outdoors | Jun 2 – Jun 8 |
| Peppers | Start seeds indoors | Apr 16 – May 17 |
| Peppers | Transplant outdoors | Jun 16 – Jul 17 |
| Eggplant | Start seeds indoors | May 3 – Jun 1 |
| Eggplant | Transplant outdoors | Jun 16 – Jul 17 |
| Cucumbers | Sow outdoors | Jun 16 – Jun 18 |
| Summer squash | Sow outdoors | Jun 2 – Jul 17 |
| Winter squash & pumpkins | Sow outdoors | Jun 16 – Jul 17 |
| Snap beans | Sow outdoors | Jun 2 – Jul 11 |
| Sweet corn | Sow outdoors | Jun 2 – Jun 8 |
| Watermelon & cantaloupe | Sow outdoors | Jun 16 – Jul 17 |
| Okra | Sow outdoors | Jun 9 – Jul 2 |
| Peas | Sow outdoors (spring) | Apr 16 – Jun 1 |
| Potatoes | Plant outdoors (spring) | Apr 16 – Jun 16 |
| Onions | Start seeds indoors (spring) | Mar 5 – Apr 1 |
| Onions | Transplant outdoors (spring) | May 3 – Jun 1 |
| Broccoli | Start seeds indoors (spring) | Mar 29 – May 2 |
| Broccoli | Transplant outdoors (spring) | May 3 – Jun 1 |
| Broccoli | Start seeds indoors (fall) | May 29 – Jun 8 |
| Broccoli | Transplant outdoors (fall) | Jun 28 – Jul 9 |
| Cabbage | Start seeds indoors (spring) | Mar 19 – Apr 16 |
| Cabbage | Transplant outdoors (spring) | Apr 16 – May 17 |
| Cabbage | Start seeds indoors (fall) | May 19 – Jun 18 |
| Cabbage | Transplant outdoors (fall) | Jun 18 – Jul 19 |
| Leaf lettuce | Sow outdoors (spring) | Apr 16 – Jul 2 |
| Leaf lettuce | Sow outdoors (fall) | Jun 18 – Aug 4 |
| Spinach | Sow outdoors (spring) | Apr 9 – May 23 |
| Spinach | Sow outdoors (fall) | Jul 5 – Aug 9 |
| Radishes | Sow outdoors (spring) | Apr 16 – Jun 6 |
| Radishes | Sow outdoors (fall) | Jun 18 – Aug 19 |
| Kale | Sow outdoors (spring) | May 3 – May 23 |
| Kale | Sow outdoors (fall) | Jun 11 – Jul 19 |
| Carrots | Sow outdoors (spring) | May 17 – Jul 2 |
| Carrots | Sow outdoors (fall) | May 19 – Jul 4 |
| Garlic | Plant outdoors (fall) | Sep 18 – Oct 19 |
Where these dates come from
ZIP code 82833 is matched to the NOAA station Big Horn, WY, 3.5 km away, at 4,208 ft elevation (172 ft lower than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Big Horn, WY (used) | 4,208 ft | May 17 | Sep 28 |
| Story, WY | 5,168 ft | May 24 | Sep 23 |
| Sheridan Co Ap, WY | 3,945 ft | May 21 | Sep 23 |
| Sheridan Fld Stn, WY | 3,750 ft | May 18 | Sep 24 |
Frost dates near Big Horn
- Story, WY 82842 · last May 24, first Sep 23
- Sheridan, WY 82801 · last May 21, first Sep 23
- Banner, WY 82832 · last May 24, first Sep 21
- Saddlestring, WY 82840 · last May 24, first Sep 23
- Wolf, WY 82844 · last May 21, first Sep 23
- Wyarno, WY 82845 · last May 21, first Sep 23
- Ranchester, WY 82839 · last May 24, first Sep 18
- Dayton, WY 82836 · last May 24, first Sep 18
Frequently asked questions
- When is the last frost in Big Horn, WY?
- For ZIP code 82833, the average last spring frost (32°F) is May 17, based on NOAA 1991-2020 climate normals for the Big Horn, WY weather station. There is a 1-in-10 chance of a frost after May 31.
- When is the first frost in Big Horn, WY?
- The average first fall frost (32°F) is September 28. There is a 1-in-10 chance of frost by September 13, so tender plants are at risk from that point on.
- How long is the growing season in 82833?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 132 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.