Frost dates for 59752Three Forks, MT
The average last spring frost in Three Forks is May 9 and the average first fall frost is September 27, giving a typical growing season of about 139 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- May 9
- Average first fall frost
- Sep 27
- Growing season
- 139 days
Safer after May 24 (1-in-10 risk)
Possible by Sep 12 (1-in-10 risk)
Last frost typically in 187 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 10 · May 24 · Jun 10 | Sep 1 · Sep 15 · Sep 30 | 112 days | 100% |
| Frost / freeze (32°F) | Apr 29 · May 9 · May 24 | Sep 12 · Sep 27 · Oct 9 | 139 days | 100% |
| Hard freeze (28°F) | Apr 12 · Apr 29 · May 10 | Sep 24 · Oct 6 · Oct 22 | 161 days | 100% |
Planting calendar for Three Forks
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 8 – Jun 14 |
| Tomatoes | Transplant outdoors | May 25 – Jun 7 |
| Peppers | Start seeds indoors | Apr 8 – May 9 |
| Peppers | Transplant outdoors | Jun 8 – Jul 9 |
| Eggplant | Start seeds indoors | Apr 25 – May 24 |
| Eggplant | Transplant outdoors | Jun 8 – Jul 9 |
| Cucumbers | Sow outdoors | Jun 8 – Jun 17 |
| Summer squash | Sow outdoors | May 25 – Jul 9 |
| Winter squash & pumpkins | Sow outdoors | Jun 8 – Jul 9 |
| Snap beans | Sow outdoors | May 25 – Jul 10 |
| Sweet corn | Sow outdoors | May 25 – Jun 7 |
| Watermelon & cantaloupe | Sow outdoors | Jun 8 – Jul 9 |
| Okra | Sow outdoors | Jun 1 – Jun 24 |
| Peas | Sow outdoors (spring) | Apr 8 – May 24 |
| Potatoes | Plant outdoors (spring) | Apr 8 – Jun 8 |
| Onions | Start seeds indoors (spring) | Feb 25 – Mar 24 |
| Onions | Transplant outdoors (spring) | Apr 25 – May 24 |
| Broccoli | Start seeds indoors (spring) | Mar 21 – Apr 24 |
| Broccoli | Transplant outdoors (spring) | Apr 25 – May 24 |
| Broccoli | Start seeds indoors (fall) | May 28 – Jun 7 |
| Broccoli | Transplant outdoors (fall) | Jun 27 – Jul 8 |
| Cabbage | Start seeds indoors (spring) | Mar 11 – Apr 8 |
| Cabbage | Transplant outdoors (spring) | Apr 8 – May 9 |
| Cabbage | Start seeds indoors (fall) | May 18 – Jun 17 |
| Cabbage | Transplant outdoors (fall) | Jun 17 – Jul 18 |
| Leaf lettuce | Sow outdoors (spring) | Apr 8 – Jun 24 |
| Leaf lettuce | Sow outdoors (fall) | Jun 17 – Aug 3 |
| Spinach | Sow outdoors (spring) | Apr 1 – May 15 |
| Spinach | Sow outdoors (fall) | Jul 4 – Aug 8 |
| Radishes | Sow outdoors (spring) | Apr 8 – May 29 |
| Radishes | Sow outdoors (fall) | Jun 17 – Aug 18 |
| Kale | Sow outdoors (spring) | Apr 25 – May 15 |
| Kale | Sow outdoors (fall) | Jun 10 – Jul 18 |
| Carrots | Sow outdoors (spring) | May 9 – Jun 24 |
| Carrots | Sow outdoors (fall) | May 18 – Jul 3 |
| Garlic | Plant outdoors (fall) | Sep 17 – Oct 18 |
Where these dates come from
ZIP code 59752 is matched to the NOAA station Trident, MT, 9 km away, at 4,036 ft elevation (39 ft lower than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Trident, MT (used) | 4,036 ft | May 9 | Sep 27 |
| Logan Landfill, MT | 4,243 ft | May 26 | Sep 15 |
| Bozeman Gallatin Fld, MT | 4,427 ft | May 26 | Sep 16 |
| Bozeman 6 W Exp Farm, MT | 4,775 ft | May 23 | Sep 23 |
Frost dates near Three Forks
- Willow Creek, MT 59760 · last May 9, first Sep 27
- Cardwell, MT 59721 · last Apr 30, first Oct 10
- Manhattan, MT 59741 · last May 26, first Sep 16
- Harrison, MT 59735 · last Apr 30, first Oct 10
- Toston, MT 59643 · last May 19, first Sep 19
- Belgrade, MT 59714 · last May 26, first Sep 16
- Bozeman, MT 59718 · last May 23, first Sep 23
- Pony, MT 59747 · last Jun 4, first Sep 18
Frequently asked questions
- When is the last frost in Three Forks, MT?
- For ZIP code 59752, the average last spring frost (32°F) is May 9, based on NOAA 1991-2020 climate normals for the Trident, MT weather station. There is a 1-in-10 chance of a frost after May 24.
- When is the first frost in Three Forks, MT?
- The average first fall frost (32°F) is September 27. There is a 1-in-10 chance of frost by September 12, so tender plants are at risk from that point on.
- How long is the growing season in 59752?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 139 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.