Frost dates for 59410Augusta, MT
The average last spring frost in Augusta is May 19 and the average first fall frost is September 21, giving a typical growing season of about 125 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- May 19
- Average first fall frost
- Sep 21
- Growing season
- 125 days
Safer after May 31 (1-in-10 risk)
Possible by Sep 4 (1-in-10 risk)
Last frost typically in 197 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 20 · Jun 3 · Jun 22 | Aug 21 · Sep 8 · Sep 22 | 96 days | 100% |
| Frost / freeze (32°F) | May 4 · May 19 · May 31 | Sep 4 · Sep 21 · Oct 4 | 125 days | 100% |
| Hard freeze (28°F) | Apr 21 · May 6 · May 22 | Sep 14 · Oct 1 · Oct 15 | 145 days | 100% |
Planting calendar for Augusta
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 18 – Jun 24 |
| Tomatoes | Transplant outdoors | Jun 4 – Jun 1 |
| Peppers | Start seeds indoors | Apr 18 – May 19 |
| Peppers | Transplant outdoors | Jun 18 – Jul 19 |
| Eggplant | Start seeds indoors | May 5 – Jun 3 |
| Eggplant | Transplant outdoors | Jun 18 – Jul 19 |
| Cucumbers | Sow outdoors | Jun 18 – Jun 11 |
| Summer squash | Sow outdoors | Jun 4 – Jul 19 |
| Winter squash & pumpkins | Sow outdoors | Jun 18 – Jul 19 |
| Snap beans | Sow outdoors | Jun 4 – Jul 4 |
| Sweet corn | Sow outdoors | Jun 4 – Jun 1 |
| Watermelon & cantaloupe | Sow outdoors | Jun 18 – Jul 19 |
| Okra | Sow outdoors | Jun 11 – Jul 4 |
| Peas | Sow outdoors (spring) | Apr 18 – Jun 3 |
| Potatoes | Plant outdoors (spring) | Apr 18 – Jun 18 |
| Onions | Start seeds indoors (spring) | Mar 7 – Apr 3 |
| Onions | Transplant outdoors (spring) | May 5 – Jun 3 |
| Broccoli | Start seeds indoors (spring) | Mar 31 – May 4 |
| Broccoli | Transplant outdoors (spring) | May 5 – Jun 3 |
| Broccoli | Start seeds indoors (fall) | May 22 – Jun 1 |
| Broccoli | Transplant outdoors (fall) | Jun 21 – Jul 2 |
| Cabbage | Start seeds indoors (spring) | Mar 21 – Apr 18 |
| Cabbage | Transplant outdoors (spring) | Apr 18 – May 19 |
| Cabbage | Start seeds indoors (fall) | May 12 – Jun 11 |
| Cabbage | Transplant outdoors (fall) | Jun 11 – Jul 12 |
| Leaf lettuce | Sow outdoors (spring) | Apr 18 – Jul 4 |
| Leaf lettuce | Sow outdoors (fall) | Jun 11 – Jul 28 |
| Spinach | Sow outdoors (spring) | Apr 11 – May 25 |
| Spinach | Sow outdoors (fall) | Jun 28 – Aug 2 |
| Radishes | Sow outdoors (spring) | Apr 18 – Jun 8 |
| Radishes | Sow outdoors (fall) | Jun 11 – Aug 12 |
| Kale | Sow outdoors (spring) | May 5 – May 25 |
| Kale | Sow outdoors (fall) | Jun 4 – Jul 12 |
| Carrots | Sow outdoors (spring) | May 19 – Jul 4 |
| Carrots | Sow outdoors (fall) | May 12 – Jun 27 |
| Garlic | Plant outdoors (fall) | Sep 11 – Oct 12 |
Where these dates come from
ZIP code 59410 is matched to the NOAA station Augusta, MT, 4.4 km away, at 4,070 ft elevation (90 ft lower than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Augusta, MT (used) | 4,070 ft | May 19 | Sep 21 |
| Rogers Pass 9 Nne, MT | 4,200 ft | May 21 | Sep 15 |
| Gibson Dam, MT | 4,590 ft | Jun 12 | Sep 8 |
| Fairfield, MT | 3,983 ft | May 13 | Sep 27 |
Frost dates near Augusta
- Fairfield, MT 59436 · last May 13, first Sep 27
- Simms, MT 59477 · last Jun 2, first Sep 10
- Fort Shaw, MT 59443 · last Jun 2, first Sep 10
- Wolf Creek, MT 59648 · last May 21, first Sep 15
- Choteau, MT 59422 · last May 28, first Sep 12
- Sun River, MT 59483 · last Jun 2, first Sep 10
- Cascade, MT 59421 · last May 21, first Sep 19
- Power, MT 59468 · last Jun 2, first Sep 10
Frequently asked questions
- When is the last frost in Augusta, MT?
- For ZIP code 59410, the average last spring frost (32°F) is May 19, based on NOAA 1991-2020 climate normals for the Augusta, MT weather station. There is a 1-in-10 chance of a frost after May 31.
- When is the first frost in Augusta, MT?
- The average first fall frost (32°F) is September 21. There is a 1-in-10 chance of frost by September 4, so tender plants are at risk from that point on.
- How long is the growing season in 59410?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 125 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.