Frost dates for 59317Broadus, MT
The average last spring frost in Broadus is May 14 and the average first fall frost is September 28, giving a typical growing season of about 134 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- May 14
- Average first fall frost
- Sep 28
- Growing season
- 134 days
Safer after May 27 (1-in-10 risk)
Possible by Sep 13 (1-in-10 risk)
Last frost typically in 199 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 14 · May 26 · Jun 8 | Sep 4 · Sep 19 · Oct 2 | 115 days | 100% |
| Frost / freeze (32°F) | May 2 · May 14 · May 27 | Sep 13 · Sep 28 · Oct 12 | 134 days | 100% |
| Hard freeze (28°F) | Apr 21 · May 3 · May 17 | Sep 20 · Oct 5 · Oct 20 | 154 days | 100% |
Planting calendar for Broadus
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 13 – Jun 19 |
| Tomatoes | Transplant outdoors | May 30 – Jun 8 |
| Peppers | Start seeds indoors | Apr 13 – May 14 |
| Peppers | Transplant outdoors | Jun 13 – Jul 14 |
| Eggplant | Start seeds indoors | Apr 30 – May 29 |
| Eggplant | Transplant outdoors | Jun 13 – Jul 14 |
| Cucumbers | Sow outdoors | Jun 13 – Jun 18 |
| Summer squash | Sow outdoors | May 30 – Jul 14 |
| Winter squash & pumpkins | Sow outdoors | Jun 13 – Jul 14 |
| Snap beans | Sow outdoors | May 30 – Jul 11 |
| Sweet corn | Sow outdoors | May 30 – Jun 8 |
| Watermelon & cantaloupe | Sow outdoors | Jun 13 – Jul 14 |
| Okra | Sow outdoors | Jun 6 – Jun 29 |
| Peas | Sow outdoors (spring) | Apr 13 – May 29 |
| Potatoes | Plant outdoors (spring) | Apr 13 – Jun 13 |
| Onions | Start seeds indoors (spring) | Mar 2 – Mar 29 |
| Onions | Transplant outdoors (spring) | Apr 30 – May 29 |
| Broccoli | Start seeds indoors (spring) | Mar 26 – Apr 29 |
| Broccoli | Transplant outdoors (spring) | Apr 30 – May 29 |
| Broccoli | Start seeds indoors (fall) | May 29 – Jun 8 |
| Broccoli | Transplant outdoors (fall) | Jun 28 – Jul 9 |
| Cabbage | Start seeds indoors (spring) | Mar 16 – Apr 13 |
| Cabbage | Transplant outdoors (spring) | Apr 13 – May 14 |
| Cabbage | Start seeds indoors (fall) | May 19 – Jun 18 |
| Cabbage | Transplant outdoors (fall) | Jun 18 – Jul 19 |
| Leaf lettuce | Sow outdoors (spring) | Apr 13 – Jun 29 |
| Leaf lettuce | Sow outdoors (fall) | Jun 18 – Aug 4 |
| Spinach | Sow outdoors (spring) | Apr 6 – May 20 |
| Spinach | Sow outdoors (fall) | Jul 5 – Aug 9 |
| Radishes | Sow outdoors (spring) | Apr 13 – Jun 3 |
| Radishes | Sow outdoors (fall) | Jun 18 – Aug 19 |
| Kale | Sow outdoors (spring) | Apr 30 – May 20 |
| Kale | Sow outdoors (fall) | Jun 11 – Jul 19 |
| Carrots | Sow outdoors (spring) | May 14 – Jun 29 |
| Carrots | Sow outdoors (fall) | May 19 – Jul 4 |
| Garlic | Plant outdoors (fall) | Sep 18 – Oct 19 |
Where these dates come from
ZIP code 59317 is matched to the NOAA station Biddle 8 Sw, MT, 29.6 km away, at 3,631 ft elevation (127 ft higher than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Biddle 8 Sw, MT (used) | 3,631 ft | May 14 | Sep 28 |
| Broadus, MT | 3,032 ft | May 16 | Sep 28 |
| Moorhead 9 Ne, MT | 3,220 ft | May 17 | Sep 22 |
| Sonnette 7 Sw, MT | 3,914 ft | May 25 | Sep 19 |
Frost dates near Broadus
- Boyes, MT 59316 · last May 16, first Sep 28
- Biddle, MT 59314 · last May 14, first Sep 28
- Olive, MT 59343 · last May 16, first Sep 28
- Weston, WY 82731 · last May 23, first Sep 18
- Powderville, MT 59345 · last May 13, first Sep 25
- Hammond, MT 59332 · last May 17, first Sep 22
- Recluse, WY 82725 · last May 21, first Sep 23
- Otter, MT 59062 · last May 25, first Sep 19
Frequently asked questions
- When is the last frost in Broadus, MT?
- For ZIP code 59317, the average last spring frost (32°F) is May 14, based on NOAA 1991-2020 climate normals for the Biddle 8 Sw, MT weather station. There is a 1-in-10 chance of a frost after May 27.
- When is the first frost in Broadus, MT?
- The average first fall frost (32°F) is September 28. There is a 1-in-10 chance of frost by September 13, so tender plants are at risk from that point on.
- How long is the growing season in 59317?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 134 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.