Frost dates for 59258Reserve, MT
The average last spring frost in Reserve is May 25 and the average first fall frost is September 14, giving a typical growing season of about 111 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- May 25
- Average first fall frost
- Sep 14
- Growing season
- 111 days
Safer after Jun 8 (1-in-10 risk)
Possible by Sep 2 (1-in-10 risk)
Last frost typically in 203 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 23 · Jun 6 · Jun 29 | Aug 21 · Sep 4 · Sep 15 | 88 days | 100% |
| Frost / freeze (32°F) | May 13 · May 25 · Jun 8 | Sep 2 · Sep 14 · Sep 25 | 111 days | 100% |
| Hard freeze (28°F) | May 3 · May 15 · May 28 | Sep 9 · Sep 22 · Oct 3 | 129 days | 100% |
Planting calendar for Reserve
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 24 – Jun 30 |
| Tomatoes | Transplant outdoors | Jun 10 – May 25 |
| Peppers | Start seeds indoors | Apr 24 – May 25 |
| Peppers | Transplant outdoors | Jun 24 – Jul 25 |
| Eggplant | Start seeds indoors | May 11 – Jun 9 |
| Eggplant | Transplant outdoors | Jun 24 – Jul 25 |
| Cucumbers | Sow outdoors | Jun 24 – Jun 4 |
| Summer squash | Sow outdoors | Jun 10 – Jul 25 |
| Winter squash & pumpkins | Sow outdoors | Jun 24 – Jul 25 |
| Snap beans | Sow outdoors | Jun 10 – Jun 27 |
| Sweet corn | Sow outdoors | Jun 10 – May 25 |
| Watermelon & cantaloupe | Sow outdoors | Jun 24 – Jul 25 |
| Okra | Sow outdoors | Jun 17 – Jul 10 |
| Peas | Sow outdoors (spring) | Apr 24 – Jun 9 |
| Potatoes | Plant outdoors (spring) | Apr 24 – Jun 24 |
| Onions | Start seeds indoors (spring) | Mar 13 – Apr 9 |
| Onions | Transplant outdoors (spring) | May 11 – Jun 9 |
| Broccoli | Start seeds indoors (spring) | Apr 6 – May 10 |
| Broccoli | Transplant outdoors (spring) | May 11 – Jun 9 |
| Broccoli | Start seeds indoors (fall) | May 15 – May 25 |
| Broccoli | Transplant outdoors (fall) | Jun 14 – Jun 25 |
| Cabbage | Start seeds indoors (spring) | Mar 27 – Apr 24 |
| Cabbage | Transplant outdoors (spring) | Apr 24 – May 25 |
| Cabbage | Start seeds indoors (fall) | May 5 – Jun 4 |
| Cabbage | Transplant outdoors (fall) | Jun 4 – Jul 5 |
| Leaf lettuce | Sow outdoors (spring) | Apr 24 – Jul 10 |
| Leaf lettuce | Sow outdoors (fall) | Jun 4 – Jul 21 |
| Spinach | Sow outdoors (spring) | Apr 17 – May 31 |
| Spinach | Sow outdoors (fall) | Jun 21 – Jul 26 |
| Radishes | Sow outdoors (spring) | Apr 24 – Jun 14 |
| Radishes | Sow outdoors (fall) | Jun 4 – Aug 5 |
| Kale | Sow outdoors (spring) | May 11 – May 31 |
| Kale | Sow outdoors (fall) | May 28 – Jul 5 |
| Carrots | Sow outdoors (spring) | May 25 – Jul 10 |
| Carrots | Sow outdoors (fall) | May 5 – Jun 20 |
| Garlic | Plant outdoors (fall) | Sep 4 – Oct 5 |
Where these dates come from
ZIP code 59258 is matched to the NOAA station Plentywood, MT, 21 km away, at 2,048 ft elevation (239 ft lower than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Plentywood, MT (used) | 2,048 ft | May 25 | Sep 14 |
| Medicine Lake 3 Se, MT | 1,942 ft | May 16 | Sep 18 |
| Redstone, MT | 2,106 ft | May 28 | Sep 7 |
| Wolf Point 34 Ne, MT | 2,643 ft | May 13 | Sep 28 |
Frost dates near Reserve
- Antelope, MT 59211 · last May 25, first Sep 14
- Medicine Lake, MT 59247 · last May 16, first Sep 18
- Plentywood, MT 59254 · last May 25, first Sep 14
- Homestead, MT 59242 · last May 16, first Sep 18
- Redstone, MT 59257 · last May 28, first Sep 7
- Dagmar, MT 59219 · last May 16, first Sep 18
- Froid, MT 59226 · last May 16, first Sep 18
- Raymond, MT 59256 · last May 19, first Sep 23
Frequently asked questions
- When is the last frost in Reserve, MT?
- For ZIP code 59258, the average last spring frost (32°F) is May 25, based on NOAA 1991-2020 climate normals for the Plentywood, MT weather station. There is a 1-in-10 chance of a frost after June 8.
- When is the first frost in Reserve, MT?
- The average first fall frost (32°F) is September 14. There is a 1-in-10 chance of frost by September 2, so tender plants are at risk from that point on.
- How long is the growing season in 59258?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 111 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.