Frost dates for 59934Trego, MT
The average last spring frost in Trego is May 16 and the average first fall frost is September 18, giving a typical growing season of about 121 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- May 16
- Average first fall frost
- Sep 18
- Growing season
- 121 days
Safer after Jun 3 (1-in-10 risk)
Possible by Sep 1 (1-in-10 risk)
Last frost typically in 194 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 18 · Jun 2 · Jun 23 | Aug 20 · Sep 4 · Sep 22 | 90 days | 100% |
| Frost / freeze (32°F) | May 3 · May 16 · Jun 3 | Sep 1 · Sep 18 · Oct 5 | 121 days | 100% |
| Hard freeze (28°F) | Apr 14 · May 1 · May 20 | Sep 15 · Oct 2 · Oct 19 | 154 days | 100% |
Planting calendar for Trego
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 15 – Jun 21 |
| Tomatoes | Transplant outdoors | Jun 1 – May 29 |
| Peppers | Start seeds indoors | Apr 15 – May 16 |
| Peppers | Transplant outdoors | Jun 15 – Jul 16 |
| Eggplant | Start seeds indoors | May 2 – May 31 |
| Eggplant | Transplant outdoors | Jun 15 – Jul 16 |
| Cucumbers | Sow outdoors | Jun 15 – Jun 8 |
| Summer squash | Sow outdoors | Jun 1 – Jul 16 |
| Winter squash & pumpkins | Sow outdoors | Jun 15 – Jul 16 |
| Snap beans | Sow outdoors | Jun 1 – Jul 1 |
| Sweet corn | Sow outdoors | Jun 1 – May 29 |
| Watermelon & cantaloupe | Sow outdoors | Jun 15 – Jul 16 |
| Okra | Sow outdoors | Jun 8 – Jul 1 |
| Peas | Sow outdoors (spring) | Apr 15 – May 31 |
| Potatoes | Plant outdoors (spring) | Apr 15 – Jun 15 |
| Onions | Start seeds indoors (spring) | Mar 4 – Mar 31 |
| Onions | Transplant outdoors (spring) | May 2 – May 31 |
| Broccoli | Start seeds indoors (spring) | Mar 28 – May 1 |
| Broccoli | Transplant outdoors (spring) | May 2 – May 31 |
| Broccoli | Start seeds indoors (fall) | May 19 – May 29 |
| Broccoli | Transplant outdoors (fall) | Jun 18 – Jun 29 |
| Cabbage | Start seeds indoors (spring) | Mar 18 – Apr 15 |
| Cabbage | Transplant outdoors (spring) | Apr 15 – May 16 |
| Cabbage | Start seeds indoors (fall) | May 9 – Jun 8 |
| Cabbage | Transplant outdoors (fall) | Jun 8 – Jul 9 |
| Leaf lettuce | Sow outdoors (spring) | Apr 15 – Jul 1 |
| Leaf lettuce | Sow outdoors (fall) | Jun 8 – Jul 25 |
| Spinach | Sow outdoors (spring) | Apr 8 – May 22 |
| Spinach | Sow outdoors (fall) | Jun 25 – Jul 30 |
| Radishes | Sow outdoors (spring) | Apr 15 – Jun 5 |
| Radishes | Sow outdoors (fall) | Jun 8 – Aug 9 |
| Kale | Sow outdoors (spring) | May 2 – May 22 |
| Kale | Sow outdoors (fall) | Jun 1 – Jul 9 |
| Carrots | Sow outdoors (spring) | May 16 – Jul 1 |
| Carrots | Sow outdoors (fall) | May 9 – Jun 24 |
| Garlic | Plant outdoors (fall) | Sep 8 – Oct 9 |
Where these dates come from
ZIP code 59934 is matched to the NOAA station Fortine 1 N, MT, 8.4 km away, at 3,000 ft elevation (120 ft lower than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Fortine 1 N, MT (used) | 3,000 ft | May 16 | Sep 18 |
| Eureka Rs, MT | 2,532 ft | May 11 | Sep 27 |
| Olney, MT | 3,165 ft | — | — |
| Polebridge, MT | 3,520 ft | — | — |
Frost dates near Trego
- Fortine, MT 59918 · last May 16, first Sep 18
- Stryker, MT 59933 · last —, first —
- Eureka, MT 59917 · last May 11, first Sep 27
- Olney, MT 59927 · last —, first —
- Rexford, MT 59930 · last May 11, first Sep 27
- Polebridge, MT 59928 · last —, first —
- Whitefish, MT 59937 · last May 16, first Sep 25
- Libby, MT 59923 · last May 23, first Sep 21
Frequently asked questions
- When is the last frost in Trego, MT?
- For ZIP code 59934, the average last spring frost (32°F) is May 16, based on NOAA 1991-2020 climate normals for the Fortine 1 N, MT weather station. There is a 1-in-10 chance of a frost after June 3.
- When is the first frost in Trego, MT?
- The average first fall frost (32°F) is September 18. There is a 1-in-10 chance of frost by September 1, so tender plants are at risk from that point on.
- How long is the growing season in 59934?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 121 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.