Frost dates for 59725Dillon, MT
The average last spring frost in Dillon is June 5 and the average first fall frost is September 13, giving a typical growing season of about 98 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- Jun 5
- Average first fall frost
- Sep 13
- Growing season
- 98 days
Safer after Jun 23 (1-in-10 risk)
Possible by Aug 29 (1-in-10 risk)
Last frost typically in 214 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) | — | — | 65 days | 100% |
| Frost / freeze (32°F) | May 18 · Jun 5 · Jun 23 | Aug 29 · Sep 13 · Sep 27 | 98 days | 100% |
| Hard freeze (28°F) | May 3 · May 16 · Jun 3 | Sep 9 · Sep 25 · Oct 8 | 130 days | 100% |
Planting calendar for Dillon
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 | May 5 – Jul 11 |
| Tomatoes | Transplant outdoors | Jun 21 – May 24 |
| Peppers | Start seeds indoors | May 5 – Jun 5 |
| Peppers | Transplant outdoors | Jul 5 – Aug 5 |
| Eggplant | Start seeds indoors | May 22 – Jun 20 |
| Eggplant | Transplant outdoors | Jul 5 – Aug 5 |
| Cucumbers | Sow outdoors | Jul 5 – Jun 3 |
| Summer squash | Sow outdoors | Jun 21 – Aug 5 |
| Winter squash & pumpkins | Sow outdoors | Jul 5 – Aug 5 |
| Snap beans | Sow outdoors | Jun 21 – Jun 26 |
| Sweet corn | Sow outdoors | Jun 21 – May 24 |
| Watermelon & cantaloupe | Sow outdoors | Jul 5 – Aug 5 |
| Okra | Sow outdoors | Jun 28 – Jul 21 |
| Peas | Sow outdoors (spring) | May 5 – Jun 20 |
| Potatoes | Plant outdoors (spring) | May 5 – Jul 5 |
| Onions | Start seeds indoors (spring) | Mar 24 – Apr 20 |
| Onions | Transplant outdoors (spring) | May 22 – Jun 20 |
| Broccoli | Start seeds indoors (spring) | Apr 17 – May 21 |
| Broccoli | Transplant outdoors (spring) | May 22 – Jun 20 |
| Broccoli | Start seeds indoors (fall) | May 14 – May 24 |
| Broccoli | Transplant outdoors (fall) | Jun 13 – Jun 24 |
| Cabbage | Start seeds indoors (spring) | Apr 7 – May 5 |
| Cabbage | Transplant outdoors (spring) | May 5 – Jun 5 |
| Cabbage | Start seeds indoors (fall) | May 4 – Jun 3 |
| Cabbage | Transplant outdoors (fall) | Jun 3 – Jul 4 |
| Leaf lettuce | Sow outdoors (spring) | May 5 – Jul 21 |
| Leaf lettuce | Sow outdoors (fall) | Jun 3 – Jul 20 |
| Spinach | Sow outdoors (spring) | Apr 28 – Jun 11 |
| Spinach | Sow outdoors (fall) | Jun 20 – Jul 25 |
| Radishes | Sow outdoors (spring) | May 5 – Jun 25 |
| Radishes | Sow outdoors (fall) | Jun 3 – Aug 4 |
| Kale | Sow outdoors (spring) | May 22 – Jun 11 |
| Kale | Sow outdoors (fall) | May 27 – Jul 4 |
| Carrots | Sow outdoors (spring) | Jun 5 – Jul 21 |
| Carrots | Sow outdoors (fall) | May 4 – Jun 19 |
| Garlic | Plant outdoors (fall) | Sep 3 – Oct 4 |
Where these dates come from
ZIP code 59725 is matched to the NOAA station Dillon U Of Montana Western, MT, 2.8 km away, at 5,129 ft elevation (44 ft higher than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Dillon U Of Montana Western, MT (used) | 5,129 ft | Jun 5 | Sep 13 |
| Dillon Ap, MT | 5,200 ft | Jun 2 | Sep 13 |
| Dillon 18 Wsw, MT | 5,971 ft | — | — |
| Glen 4 N, MT | 5,054 ft | — | — |
Frost dates near Dillon
- Glen, MT 59732 · last —, first —
- Twin Bridges, MT 59754 · last Jun 8, first Sep 2
- Polaris, MT 59746 · last —, first —
- Sheridan, MT 59749 · last May 24, first Sep 22
- Melrose, MT 59743 · last Jun 10, first Sep 7
- Alder, MT 59710 · last Jun 6, first Sep 14
- Virginia City, MT 59755 · last Jun 4, first Sep 18
- Dell, MT 59724 · last Jun 11, first Sep 10
Frequently asked questions
- When is the last frost in Dillon, MT?
- For ZIP code 59725, the average last spring frost (32°F) is June 5, based on NOAA 1991-2020 climate normals for the Dillon U Of Montana Western, MT weather station. There is a 1-in-10 chance of a frost after June 23.
- When is the first frost in Dillon, MT?
- The average first fall frost (32°F) is September 13. There is a 1-in-10 chance of frost by August 29, so tender plants are at risk from that point on.
- How long is the growing season in 59725?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 98 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.