Frost dates for 59003Ashland, MT
The average last spring frost in Ashland is May 18 and the average first fall frost is September 22, giving a typical growing season of about 126 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- May 18
- Average first fall frost
- Sep 22
- Growing season
- 126 days
Safer after May 30 (1-in-10 risk)
Possible by Sep 8 (1-in-10 risk)
Last frost typically in 196 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 · May 30 · Jun 15 | Aug 27 · Sep 10 · Sep 26 | 103 days | 100% |
| Frost / freeze (32°F) | May 6 · May 18 · May 30 | Sep 8 · Sep 22 · Oct 5 | 126 days | 100% |
| Hard freeze (28°F) | Apr 25 · May 7 · May 19 | Sep 17 · Oct 2 · Oct 16 | 148 days | 100% |
Planting calendar for Ashland
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 17 – Jun 23 |
| Tomatoes | Transplant outdoors | Jun 3 – Jun 2 |
| Peppers | Start seeds indoors | Apr 17 – May 18 |
| Peppers | Transplant outdoors | Jun 17 – Jul 18 |
| Eggplant | Start seeds indoors | May 4 – Jun 2 |
| Eggplant | Transplant outdoors | Jun 17 – Jul 18 |
| Cucumbers | Sow outdoors | Jun 17 – Jun 12 |
| Summer squash | Sow outdoors | Jun 3 – Jul 18 |
| Winter squash & pumpkins | Sow outdoors | Jun 17 – Jul 18 |
| Snap beans | Sow outdoors | Jun 3 – Jul 5 |
| Sweet corn | Sow outdoors | Jun 3 – Jun 2 |
| Watermelon & cantaloupe | Sow outdoors | Jun 17 – Jul 18 |
| Okra | Sow outdoors | Jun 10 – Jul 3 |
| Peas | Sow outdoors (spring) | Apr 17 – Jun 2 |
| Potatoes | Plant outdoors (spring) | Apr 17 – Jun 17 |
| Onions | Start seeds indoors (spring) | Mar 6 – Apr 2 |
| Onions | Transplant outdoors (spring) | May 4 – Jun 2 |
| Broccoli | Start seeds indoors (spring) | Mar 30 – May 3 |
| Broccoli | Transplant outdoors (spring) | May 4 – Jun 2 |
| Broccoli | Start seeds indoors (fall) | May 23 – Jun 2 |
| Broccoli | Transplant outdoors (fall) | Jun 22 – Jul 3 |
| Cabbage | Start seeds indoors (spring) | Mar 20 – Apr 17 |
| Cabbage | Transplant outdoors (spring) | Apr 17 – May 18 |
| Cabbage | Start seeds indoors (fall) | May 13 – Jun 12 |
| Cabbage | Transplant outdoors (fall) | Jun 12 – Jul 13 |
| Leaf lettuce | Sow outdoors (spring) | Apr 17 – Jul 3 |
| Leaf lettuce | Sow outdoors (fall) | Jun 12 – Jul 29 |
| Spinach | Sow outdoors (spring) | Apr 10 – May 24 |
| Spinach | Sow outdoors (fall) | Jun 29 – Aug 3 |
| Radishes | Sow outdoors (spring) | Apr 17 – Jun 7 |
| Radishes | Sow outdoors (fall) | Jun 12 – Aug 13 |
| Kale | Sow outdoors (spring) | May 4 – May 24 |
| Kale | Sow outdoors (fall) | Jun 5 – Jul 13 |
| Carrots | Sow outdoors (spring) | May 18 – Jul 3 |
| Carrots | Sow outdoors (fall) | May 13 – Jun 28 |
| Garlic | Plant outdoors (fall) | Sep 12 – Oct 13 |
Where these dates come from
ZIP code 59003 is matched to the NOAA station Brandenberg, MT, 26.2 km away, at 2,770 ft elevation (340 ft lower than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Brandenberg, MT (used) | 2,770 ft | May 18 | Sep 22 |
| Sonnette 7 Sw, MT | 3,914 ft | May 25 | Sep 19 |
| Colstrip, MT | 3,218 ft | May 15 | Sep 30 |
| Busby, MT | 3,430 ft | May 23 | Sep 15 |
Frost dates near Ashland
- Ashland, MT 59004 · last May 18, first Sep 22
- Lame Deer, MT 59043 · last May 23, first Sep 15
- Birney, MT 59012 · last May 23, first Sep 15
- Busby, MT 59016 · last May 23, first Sep 15
- Colstrip, MT 59323 · last May 15, first Sep 30
- Volborg, MT 59351 · last May 16, first Sep 28
- Otter, MT 59062 · last May 25, first Sep 19
- Olive, MT 59343 · last May 16, first Sep 28
Frequently asked questions
- When is the last frost in Ashland, MT?
- For ZIP code 59003, the average last spring frost (32°F) is May 18, based on NOAA 1991-2020 climate normals for the Brandenberg, MT weather station. There is a 1-in-10 chance of a frost after May 30.
- When is the first frost in Ashland, MT?
- The average first fall frost (32°F) is September 22. There is a 1-in-10 chance of frost by September 8, so tender plants are at risk from that point on.
- How long is the growing season in 59003?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 126 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.