Frost dates for 59012Birney, MT
The average last spring frost in Birney is May 23 and the average first fall frost is September 15, giving a typical growing season of about 113 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- May 23
- Average first fall frost
- Sep 15
- Growing season
- 113 days
Safer after Jun 7 (1-in-10 risk)
Possible by Sep 1 (1-in-10 risk)
Last frost typically in 201 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 24 · Jun 8 · Jul 2 | Aug 20 · Sep 4 · Sep 18 | 86 days | 100% |
| Frost / freeze (32°F) | May 12 · May 23 · Jun 7 | Sep 1 · Sep 15 · Oct 1 | 113 days | 100% |
| Hard freeze (28°F) | Apr 30 · May 11 · May 24 | Sep 11 · Sep 27 · Oct 11 | 136 days | 100% |
Planting calendar for Birney
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 22 – Jun 28 |
| Tomatoes | Transplant outdoors | Jun 8 – May 26 |
| Peppers | Start seeds indoors | Apr 22 – May 23 |
| Peppers | Transplant outdoors | Jun 22 – Jul 23 |
| Eggplant | Start seeds indoors | May 9 – Jun 7 |
| Eggplant | Transplant outdoors | Jun 22 – Jul 23 |
| Cucumbers | Sow outdoors | Jun 22 – Jun 5 |
| Summer squash | Sow outdoors | Jun 8 – Jul 23 |
| Winter squash & pumpkins | Sow outdoors | Jun 22 – Jul 23 |
| Snap beans | Sow outdoors | Jun 8 – Jun 28 |
| Sweet corn | Sow outdoors | Jun 8 – May 26 |
| Watermelon & cantaloupe | Sow outdoors | Jun 22 – Jul 23 |
| Okra | Sow outdoors | Jun 15 – Jul 8 |
| Peas | Sow outdoors (spring) | Apr 22 – Jun 7 |
| Potatoes | Plant outdoors (spring) | Apr 22 – Jun 22 |
| Onions | Start seeds indoors (spring) | Mar 11 – Apr 7 |
| Onions | Transplant outdoors (spring) | May 9 – Jun 7 |
| Broccoli | Start seeds indoors (spring) | Apr 4 – May 8 |
| Broccoli | Transplant outdoors (spring) | May 9 – Jun 7 |
| Broccoli | Start seeds indoors (fall) | May 16 – May 26 |
| Broccoli | Transplant outdoors (fall) | Jun 15 – Jun 26 |
| Cabbage | Start seeds indoors (spring) | Mar 25 – Apr 22 |
| Cabbage | Transplant outdoors (spring) | Apr 22 – May 23 |
| Cabbage | Start seeds indoors (fall) | May 6 – Jun 5 |
| Cabbage | Transplant outdoors (fall) | Jun 5 – Jul 6 |
| Leaf lettuce | Sow outdoors (spring) | Apr 22 – Jul 8 |
| Leaf lettuce | Sow outdoors (fall) | Jun 5 – Jul 22 |
| Spinach | Sow outdoors (spring) | Apr 15 – May 29 |
| Spinach | Sow outdoors (fall) | Jun 22 – Jul 27 |
| Radishes | Sow outdoors (spring) | Apr 22 – Jun 12 |
| Radishes | Sow outdoors (fall) | Jun 5 – Aug 6 |
| Kale | Sow outdoors (spring) | May 9 – May 29 |
| Kale | Sow outdoors (fall) | May 29 – Jul 6 |
| Carrots | Sow outdoors (spring) | May 23 – Jul 8 |
| Carrots | Sow outdoors (fall) | May 6 – Jun 21 |
| Garlic | Plant outdoors (fall) | Sep 5 – Oct 6 |
Where these dates come from
ZIP code 59012 is matched to the NOAA station Busby, MT, 45 km away, at 3,430 ft elevation (31 ft higher than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Busby, MT (used) | 3,430 ft | May 23 | Sep 15 |
| Sonnette 7 Sw, MT | 3,914 ft | May 25 | Sep 19 |
| Leiter 9N, WY | 4,160 ft | May 14 | Sep 30 |
| Sheridan Fld Stn, WY | 3,750 ft | May 18 | Sep 24 |
Frost dates near Birney
- Decker, MT 59025 · last May 21, first Sep 23
- Lame Deer, MT 59043 · last May 23, first Sep 15
- Otter, MT 59062 · last May 25, first Sep 19
- Ashland, MT 59003 · last May 18, first Sep 22
- Busby, MT 59016 · last May 23, first Sep 15
- Wyarno, WY 82845 · last May 21, first Sep 23
- Leiter, WY 82837 · last May 24, first Sep 16
- Sheridan, WY 82801 · last May 21, first Sep 23
Frequently asked questions
- When is the last frost in Birney, MT?
- For ZIP code 59012, the average last spring frost (32°F) is May 23, based on NOAA 1991-2020 climate normals for the Busby, MT weather station. There is a 1-in-10 chance of a frost after June 7.
- When is the first frost in Birney, MT?
- The average first fall frost (32°F) is September 15. 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 59012?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 113 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.