Frost dates for 82902Rock Springs, WY
The average last spring frost in Rock Springs is May 24 and the average first fall frost is September 24, giving a typical growing season of about 121 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- May 24
- Average first fall frost
- Sep 24
- Growing season
- 121 days
Safer after Jun 9 (1-in-10 risk)
Possible by Sep 9 (1-in-10 risk)
Last frost typically in 209 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 24 · Jun 6 · Jun 21 | Sep 2 · Sep 14 · Sep 25 | 97 days | 100% |
| Frost / freeze (32°F) | May 8 · May 24 · Jun 9 | Sep 9 · Sep 24 · Oct 4 | 121 days | 100% |
| Hard freeze (28°F) | Apr 25 · May 9 · May 26 | Sep 19 · Oct 3 · Oct 17 | 146 days | 100% |
Planting calendar for Rock Springs
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 23 – Jun 29 |
| Tomatoes | Transplant outdoors | Jun 9 – Jun 4 |
| Peppers | Start seeds indoors | Apr 23 – May 24 |
| Peppers | Transplant outdoors | Jun 23 – Jul 24 |
| Eggplant | Start seeds indoors | May 10 – Jun 8 |
| Eggplant | Transplant outdoors | Jun 23 – Jul 24 |
| Cucumbers | Sow outdoors | Jun 23 – Jun 14 |
| Summer squash | Sow outdoors | Jun 9 – Jul 24 |
| Winter squash & pumpkins | Sow outdoors | Jun 23 – Jul 24 |
| Snap beans | Sow outdoors | Jun 9 – Jul 7 |
| Sweet corn | Sow outdoors | Jun 9 – Jun 4 |
| Watermelon & cantaloupe | Sow outdoors | Jun 23 – Jul 24 |
| Okra | Sow outdoors | Jun 16 – Jul 9 |
| Peas | Sow outdoors (spring) | Apr 23 – Jun 8 |
| Potatoes | Plant outdoors (spring) | Apr 23 – Jun 23 |
| Onions | Start seeds indoors (spring) | Mar 12 – Apr 8 |
| Onions | Transplant outdoors (spring) | May 10 – Jun 8 |
| Broccoli | Start seeds indoors (spring) | Apr 5 – May 9 |
| Broccoli | Transplant outdoors (spring) | May 10 – Jun 8 |
| Broccoli | Start seeds indoors (fall) | May 25 – Jun 4 |
| Broccoli | Transplant outdoors (fall) | Jun 24 – Jul 5 |
| Cabbage | Start seeds indoors (spring) | Mar 26 – Apr 23 |
| Cabbage | Transplant outdoors (spring) | Apr 23 – May 24 |
| Cabbage | Start seeds indoors (fall) | May 15 – Jun 14 |
| Cabbage | Transplant outdoors (fall) | Jun 14 – Jul 15 |
| Leaf lettuce | Sow outdoors (spring) | Apr 23 – Jul 9 |
| Leaf lettuce | Sow outdoors (fall) | Jun 14 – Jul 31 |
| Spinach | Sow outdoors (spring) | Apr 16 – May 30 |
| Spinach | Sow outdoors (fall) | Jul 1 – Aug 5 |
| Radishes | Sow outdoors (spring) | Apr 23 – Jun 13 |
| Radishes | Sow outdoors (fall) | Jun 14 – Aug 15 |
| Kale | Sow outdoors (spring) | May 10 – May 30 |
| Kale | Sow outdoors (fall) | Jun 7 – Jul 15 |
| Carrots | Sow outdoors (spring) | May 24 – Jul 9 |
| Carrots | Sow outdoors (fall) | May 15 – Jun 30 |
| Garlic | Plant outdoors (fall) | Sep 14 – Oct 15 |
Where these dates come from
ZIP code 82902 is matched to the NOAA station Rock Springs Fire Dept, WY, 3.2 km away, at 6,270 ft elevation (118 ft lower than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Rock Springs Fire Dept, WY (used) | 6,270 ft | May 24 | Sep 24 |
| Rock Springs Ap, WY | 6,741 ft | May 22 | Sep 28 |
| Green Rvr, WY | 6,160 ft | May 24 | Sep 22 |
| Buckboard Marina, WY | 6,080 ft | May 24 | Sep 23 |
Frost dates near Rock Springs
- Rock Springs, WY 82901 · last May 24, first Sep 24
- Reliance, WY 82943 · last May 22, first Sep 28
- Green River, WY 82935 · last May 24, first Sep 22
- Superior, WY 82945 · last May 22, first Sep 28
- Point Of Rocks, WY 82942 · last May 22, first Sep 28
- Little America, WY 82929 · last May 24, first Sep 22
- Farson, WY 82932 · last —, first —
- Granger, WY 82934 · last May 24, first Sep 22
Frequently asked questions
- When is the last frost in Rock Springs, WY?
- For ZIP code 82902, the average last spring frost (32°F) is May 24, based on NOAA 1991-2020 climate normals for the Rock Springs Fire Dept, WY weather station. There is a 1-in-10 chance of a frost after June 9.
- When is the first frost in Rock Springs, WY?
- The average first fall frost (32°F) is September 24. There is a 1-in-10 chance of frost by September 9, so tender plants are at risk from that point on.
- How long is the growing season in 82902?
- 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.