Frost dates for 59724Dell, MT
The average last spring frost in Dell is June 11 and the average first fall frost is September 10, giving a typical growing season of about 89 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- Jun 11
- Average first fall frost
- Sep 10
- Growing season
- 89 days
Safer after Jun 30 (1-in-10 risk)
Possible by Aug 27 (1-in-10 risk)
Last frost typically in 227 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) | — | — | 60 days | 100% |
| Frost / freeze (32°F) | May 24 · Jun 11 · Jun 30 | Aug 27 · Sep 10 · Sep 24 | 89 days | 100% |
| Hard freeze (28°F) | May 4 · May 21 · Jun 13 | Sep 7 · Sep 23 · Oct 7 | 121 days | 100% |
Planting calendar for Dell
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 11 – Jul 17 |
| Tomatoes | Transplant outdoors | Jun 27 – May 21 |
| Peppers | Start seeds indoors | May 11 – Jun 11 |
| Peppers | Transplant outdoors | Jul 11 – Aug 11 |
| Eggplant | Start seeds indoors | May 28 – Jun 26 |
| Eggplant | Transplant outdoors | Jul 11 – Aug 11 |
| Cucumbers | Sow outdoors | Jul 11 – May 31 |
| Summer squash | Sow outdoors | Jun 27 – Aug 11 |
| Winter squash & pumpkins | Sow outdoors | Jul 11 – Aug 11 |
| Snap beans | Sow outdoors | Jun 27 – Jun 23 |
| Sweet corn | Sow outdoors | Jun 27 – May 21 |
| Watermelon & cantaloupe | Sow outdoors | Jul 11 – Aug 11 |
| Okra | Sow outdoors | Jul 4 – Jul 27 |
| Peas | Sow outdoors (spring) | May 11 – Jun 26 |
| Potatoes | Plant outdoors (spring) | May 11 – Jul 11 |
| Onions | Start seeds indoors (spring) | Mar 30 – Apr 26 |
| Onions | Transplant outdoors (spring) | May 28 – Jun 26 |
| Broccoli | Start seeds indoors (spring) | Apr 23 – May 27 |
| Broccoli | Transplant outdoors (spring) | May 28 – Jun 26 |
| Broccoli | Start seeds indoors (fall) | May 11 – May 21 |
| Broccoli | Transplant outdoors (fall) | Jun 10 – Jun 21 |
| Cabbage | Start seeds indoors (spring) | Apr 13 – May 11 |
| Cabbage | Transplant outdoors (spring) | May 11 – Jun 11 |
| Cabbage | Start seeds indoors (fall) | May 1 – May 31 |
| Cabbage | Transplant outdoors (fall) | May 31 – Jul 1 |
| Leaf lettuce | Sow outdoors (spring) | May 11 – Jul 27 |
| Leaf lettuce | Sow outdoors (fall) | May 31 – Jul 17 |
| Spinach | Sow outdoors (spring) | May 4 – Jun 17 |
| Spinach | Sow outdoors (fall) | Jun 17 – Jul 22 |
| Radishes | Sow outdoors (spring) | May 11 – Jul 1 |
| Radishes | Sow outdoors (fall) | May 31 – Aug 1 |
| Kale | Sow outdoors (spring) | May 28 – Jun 17 |
| Kale | Sow outdoors (fall) | May 24 – Jul 1 |
| Carrots | Sow outdoors (spring) | Jun 11 – Jul 27 |
| Carrots | Sow outdoors (fall) | May 1 – Jun 16 |
| Garlic | Plant outdoors (fall) | Aug 31 – Oct 1 |
Where these dates come from
ZIP code 59724 is matched to the NOAA station Lima, MT, 13 km away, at 6,279 ft elevation (265 ft higher than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Lima, MT (used) | 6,279 ft | Jun 11 | Sep 10 |
| Small 6N, ID | 5,740 ft | Jun 5 | Sep 20 |
| Leadore #2, ID | 6,000 ft | — | — |
| Dillon 18 Wsw, MT | 5,971 ft | — | — |
Frost dates near Dell
- Lima, MT 59739 · last Jun 11, first Sep 10
- Dillon, MT 59725 · last Jun 5, first Sep 13
- Spencer, ID 83446 · last May 18, first Sep 30
- Leadore, ID 83464 · last —, first —
- Dubois, ID 83423 · last May 18, first Sep 30
- Alder, MT 59710 · last Jun 6, first Sep 14
- Lemhi, ID 83465 · last Jun 12, first Sep 6
- Polaris, MT 59746 · last —, first —
Frequently asked questions
- When is the last frost in Dell, MT?
- For ZIP code 59724, the average last spring frost (32°F) is June 11, based on NOAA 1991-2020 climate normals for the Lima, MT weather station. There is a 1-in-10 chance of a frost after June 30.
- When is the first frost in Dell, MT?
- The average first fall frost (32°F) is September 10. There is a 1-in-10 chance of frost by August 27, so tender plants are at risk from that point on.
- How long is the growing season in 59724?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 89 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.