Frost dates for 59482Sunburst, MT
The average last spring frost in Sunburst is May 17 and the average first fall frost is September 25, giving a typical growing season of about 129 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- May 17
- Average first fall frost
- Sep 25
- Growing season
- 129 days
Safer after May 31 (1-in-10 risk)
Possible by Sep 9 (1-in-10 risk)
Last frost typically in 202 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 17 · Jun 2 · Jun 29 | Aug 26 · Sep 13 · Sep 25 | 99 days | 100% |
| Frost / freeze (32°F) | May 2 · May 17 · May 31 | Sep 9 · Sep 25 · Oct 6 | 129 days | 100% |
| Hard freeze (28°F) | Apr 19 · May 5 · May 20 | Sep 22 · Oct 4 · Oct 18 | 152 days | 100% |
Planting calendar for Sunburst
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 5 |
| 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 15 |
| Summer squash | Sow outdoors | Jun 2 – Jul 17 |
| Winter squash & pumpkins | Sow outdoors | Jun 16 – Jul 17 |
| Snap beans | Sow outdoors | Jun 2 – Jul 8 |
| Sweet corn | Sow outdoors | Jun 2 – Jun 5 |
| 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 26 – Jun 5 |
| Broccoli | Transplant outdoors (fall) | Jun 25 – Jul 6 |
| Cabbage | Start seeds indoors (spring) | Mar 19 – Apr 16 |
| Cabbage | Transplant outdoors (spring) | Apr 16 – May 17 |
| Cabbage | Start seeds indoors (fall) | May 16 – Jun 15 |
| Cabbage | Transplant outdoors (fall) | Jun 15 – Jul 16 |
| Leaf lettuce | Sow outdoors (spring) | Apr 16 – Jul 2 |
| Leaf lettuce | Sow outdoors (fall) | Jun 15 – Aug 1 |
| Spinach | Sow outdoors (spring) | Apr 9 – May 23 |
| Spinach | Sow outdoors (fall) | Jul 2 – Aug 6 |
| Radishes | Sow outdoors (spring) | Apr 16 – Jun 6 |
| Radishes | Sow outdoors (fall) | Jun 15 – Aug 16 |
| Kale | Sow outdoors (spring) | May 3 – May 23 |
| Kale | Sow outdoors (fall) | Jun 8 – Jul 16 |
| Carrots | Sow outdoors (spring) | May 17 – Jul 2 |
| Carrots | Sow outdoors (fall) | May 16 – Jul 1 |
| Garlic | Plant outdoors (fall) | Sep 15 – Oct 16 |
Where these dates come from
ZIP code 59482 is matched to the NOAA station Sunburst 8 E, MT, 4.1 km away, at 3,700 ft elevation (75 ft higher than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Sunburst 8 E, MT (used) | 3,700 ft | May 17 | Sep 25 |
| Sweetgrass, MT | 3,510 ft | May 15 | Sep 25 |
| Dunkirk 19Nne, MT | 3,323 ft | May 23 | Sep 14 |
| Goldbutte 7 N, MT | 3,498 ft | — | — |
Frost dates near Sunburst
- Oilmont, MT 59466 · last May 17, first Sep 25
- Kevin, MT 59454 · last May 23, first Sep 16
- Galata, MT 59444 · last May 23, first Sep 14
- Sweet Grass, MT 59484 · last May 15, first Sep 25
- Shelby, MT 59474 · last May 23, first Sep 16
- Ethridge, MT 59435 · last May 23, first Sep 16
- Whitlash, MT 59545 · last —, first —
- Cut Bank, MT 59427 · last May 24, first Sep 15
Frequently asked questions
- When is the last frost in Sunburst, MT?
- For ZIP code 59482, the average last spring frost (32°F) is May 17, based on NOAA 1991-2020 climate normals for the Sunburst 8 E, MT weather station. There is a 1-in-10 chance of a frost after May 31.
- When is the first frost in Sunburst, MT?
- The average first fall frost (32°F) is September 25. 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 59482?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 129 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.