Frost dates for 59086Wilsall, MT
The average last spring frost in Wilsall is June 4 and the average first fall frost is September 6, giving a typical growing season of about 92 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- Jun 4
- Average first fall frost
- Sep 6
- Growing season
- 92 days
Safer after Jun 23 (1-in-10 risk)
Possible by Aug 28 (1-in-10 risk)
Last frost typically in 215 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) | Jun 6 · Jun 21 · Jul 7 | Aug 19 · Sep 1 · Sep 9 | 70 days | 100% |
| Frost / freeze (32°F) | May 19 · Jun 4 · Jun 23 | Aug 28 · Sep 6 · Sep 15 | 92 days | 100% |
| Hard freeze (28°F) | May 4 · May 16 · Jun 2 | Sep 3 · Sep 13 · Sep 23 | 117 days | 100% |
Planting calendar for Wilsall
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 4 – Jul 10 |
| Tomatoes | Transplant outdoors | Jun 20 – May 17 |
| Peppers | Start seeds indoors | May 4 – Jun 4 |
| Peppers | Transplant outdoors | Jul 4 – Aug 4 |
| Eggplant | Start seeds indoors | May 21 – Jun 19 |
| Eggplant | Transplant outdoors | Jul 4 – Aug 4 |
| Cucumbers | Sow outdoors | Jul 4 – May 27 |
| Summer squash | Sow outdoors | Jun 20 – Aug 4 |
| Winter squash & pumpkins | Sow outdoors | Jul 4 – Aug 4 |
| Snap beans | Sow outdoors | Jun 20 – Jun 19 |
| Sweet corn | Sow outdoors | Jun 20 – May 17 |
| Watermelon & cantaloupe | Sow outdoors | Jul 4 – Aug 4 |
| Okra | Sow outdoors | Jun 27 – Jul 20 |
| Peas | Sow outdoors (spring) | May 4 – Jun 19 |
| Potatoes | Plant outdoors (spring) | May 4 – Jul 4 |
| Onions | Start seeds indoors (spring) | Mar 23 – Apr 19 |
| Onions | Transplant outdoors (spring) | May 21 – Jun 19 |
| Broccoli | Start seeds indoors (spring) | Apr 16 – May 20 |
| Broccoli | Transplant outdoors (spring) | May 21 – Jun 19 |
| Broccoli | Start seeds indoors (fall) | May 7 – May 17 |
| Broccoli | Transplant outdoors (fall) | Jun 6 – Jun 17 |
| Cabbage | Start seeds indoors (spring) | Apr 6 – May 4 |
| Cabbage | Transplant outdoors (spring) | May 4 – Jun 4 |
| Cabbage | Start seeds indoors (fall) | Apr 27 – May 27 |
| Cabbage | Transplant outdoors (fall) | May 27 – Jun 27 |
| Leaf lettuce | Sow outdoors (spring) | May 4 – Jul 20 |
| Leaf lettuce | Sow outdoors (fall) | May 27 – Jul 13 |
| Spinach | Sow outdoors (spring) | Apr 27 – Jun 10 |
| Spinach | Sow outdoors (fall) | Jun 13 – Jul 18 |
| Radishes | Sow outdoors (spring) | May 4 – Jun 24 |
| Radishes | Sow outdoors (fall) | May 27 – Jul 28 |
| Kale | Sow outdoors (spring) | May 21 – Jun 10 |
| Kale | Sow outdoors (fall) | May 20 – Jun 27 |
| Carrots | Sow outdoors (spring) | Jun 4 – Jul 20 |
| Carrots | Sow outdoors (fall) | Apr 27 – Jun 12 |
| Garlic | Plant outdoors (fall) | Aug 27 – Sep 27 |
Where these dates come from
ZIP code 59086 is matched to the NOAA station Wilsall 1S, MT, 5.8 km away, at 5,015 ft elevation (22 ft higher than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Wilsall 1S, MT (used) | 5,015 ft | Jun 4 | Sep 6 |
| Wilsall 8 Ene, MT | 5,865 ft | Jun 8 | Sep 7 |
| Livingston Mission Fld, MT | 4,643 ft | May 27 | Sep 14 |
| Lennep 5 Sw, MT | 5,600 ft | — | — |
Frost dates near Wilsall
- Clyde Park, MT 59018 · last May 27, first Sep 14
- Livingston, MT 59047 · last May 27, first Sep 14
- Springdale, MT 59082 · last May 14, first Sep 26
- Ringling, MT 59642 · last —, first —
- Bozeman, MT 59717 · last —, first —
- Belgrade, MT 59714 · last May 26, first Sep 16
- Big Timber, MT 59011 · last May 14, first Sep 26
- Manhattan, MT 59741 · last May 26, first Sep 16
Frequently asked questions
- When is the last frost in Wilsall, MT?
- For ZIP code 59086, the average last spring frost (32°F) is June 4, based on NOAA 1991-2020 climate normals for the Wilsall 1S, MT weather station. There is a 1-in-10 chance of a frost after June 23.
- When is the first frost in Wilsall, MT?
- The average first fall frost (32°F) is September 6. There is a 1-in-10 chance of frost by August 28, so tender plants are at risk from that point on.
- How long is the growing season in 59086?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 92 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.