Frost dates for 59436Fairfield, MT
The average last spring frost in Fairfield is May 13 and the average first fall frost is September 27, giving a typical growing season of about 135 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- May 13
- Average first fall frost
- Sep 27
- Growing season
- 135 days
Safer after Jun 1 (1-in-10 risk)
Possible by Sep 14 (1-in-10 risk)
Last frost typically in 191 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 31 · Jun 14 | Sep 1 · Sep 15 · Sep 29 | 108 days | 100% |
| Frost / freeze (32°F) | Apr 28 · May 13 · Jun 1 | Sep 14 · Sep 27 · Oct 9 | 135 days | 100% |
| Hard freeze (28°F) | Apr 14 · Apr 30 · May 14 | Sep 24 · Oct 7 · Oct 23 | 160 days | 100% |
Planting calendar for Fairfield
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 12 – Jun 18 |
| Tomatoes | Transplant outdoors | May 29 – Jun 7 |
| Peppers | Start seeds indoors | Apr 12 – May 13 |
| Peppers | Transplant outdoors | Jun 12 – Jul 13 |
| Eggplant | Start seeds indoors | Apr 29 – May 28 |
| Eggplant | Transplant outdoors | Jun 12 – Jul 13 |
| Cucumbers | Sow outdoors | Jun 12 – Jun 17 |
| Summer squash | Sow outdoors | May 29 – Jul 13 |
| Winter squash & pumpkins | Sow outdoors | Jun 12 – Jul 13 |
| Snap beans | Sow outdoors | May 29 – Jul 10 |
| Sweet corn | Sow outdoors | May 29 – Jun 7 |
| Watermelon & cantaloupe | Sow outdoors | Jun 12 – Jul 13 |
| Okra | Sow outdoors | Jun 5 – Jun 28 |
| Peas | Sow outdoors (spring) | Apr 12 – May 28 |
| Potatoes | Plant outdoors (spring) | Apr 12 – Jun 12 |
| Onions | Start seeds indoors (spring) | Mar 1 – Mar 28 |
| Onions | Transplant outdoors (spring) | Apr 29 – May 28 |
| Broccoli | Start seeds indoors (spring) | Mar 25 – Apr 28 |
| Broccoli | Transplant outdoors (spring) | Apr 29 – May 28 |
| Broccoli | Start seeds indoors (fall) | May 28 – Jun 7 |
| Broccoli | Transplant outdoors (fall) | Jun 27 – Jul 8 |
| Cabbage | Start seeds indoors (spring) | Mar 15 – Apr 12 |
| Cabbage | Transplant outdoors (spring) | Apr 12 – May 13 |
| Cabbage | Start seeds indoors (fall) | May 18 – Jun 17 |
| Cabbage | Transplant outdoors (fall) | Jun 17 – Jul 18 |
| Leaf lettuce | Sow outdoors (spring) | Apr 12 – Jun 28 |
| Leaf lettuce | Sow outdoors (fall) | Jun 17 – Aug 3 |
| Spinach | Sow outdoors (spring) | Apr 5 – May 19 |
| Spinach | Sow outdoors (fall) | Jul 4 – Aug 8 |
| Radishes | Sow outdoors (spring) | Apr 12 – Jun 2 |
| Radishes | Sow outdoors (fall) | Jun 17 – Aug 18 |
| Kale | Sow outdoors (spring) | Apr 29 – May 19 |
| Kale | Sow outdoors (fall) | Jun 10 – Jul 18 |
| Carrots | Sow outdoors (spring) | May 13 – Jun 28 |
| Carrots | Sow outdoors (fall) | May 18 – Jul 3 |
| Garlic | Plant outdoors (fall) | Sep 17 – Oct 18 |
Where these dates come from
ZIP code 59436 is matched to the NOAA station Fairfield, MT, 1.2 km away, at 3,983 ft elevation (26 ft lower than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Fairfield, MT (used) | 3,983 ft | May 13 | Sep 27 |
| Sun Rvr 4 S, MT | 3,600 ft | Jun 2 | Sep 10 |
| Choteau, MT | 3,845 ft | May 28 | Sep 12 |
| Choteau 8Ne, MT | 3,741 ft | May 20 | Sep 22 |
Frost dates near Fairfield
- Simms, MT 59477 · last Jun 2, first Sep 10
- Fort Shaw, MT 59443 · last Jun 2, first Sep 10
- Power, MT 59468 · last Jun 2, first Sep 10
- Sun River, MT 59483 · last Jun 2, first Sep 10
- Choteau, MT 59422 · last May 28, first Sep 12
- Vaughn, MT 59487 · last Jun 2, first Sep 10
- Augusta, MT 59410 · last May 19, first Sep 21
- Dutton, MT 59433 · last May 20, first Sep 19
Frequently asked questions
- When is the last frost in Fairfield, MT?
- For ZIP code 59436, the average last spring frost (32°F) is May 13, based on NOAA 1991-2020 climate normals for the Fairfield, MT weather station. There is a 1-in-10 chance of a frost after June 1.
- When is the first frost in Fairfield, MT?
- The average first fall frost (32°F) is September 27. There is a 1-in-10 chance of frost by September 14, so tender plants are at risk from that point on.
- How long is the growing season in 59436?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 135 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.