Frost dates for 59039Ingomar, MT
The average last spring frost in Ingomar is May 21 and the average first fall frost is September 19, giving a typical growing season of about 120 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- May 21
- Average first fall frost
- Sep 19
- Growing season
- 120 days
Safer after Jun 4 (1-in-10 risk)
Possible by Sep 6 (1-in-10 risk)
Last frost typically in 206 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 17 · Jun 2 · Jun 19 | Aug 24 · Sep 9 · Sep 23 | 96 days | 100% |
| Frost / freeze (32°F) | May 8 · May 21 · Jun 4 | Sep 6 · Sep 19 · Oct 2 | 120 days | 100% |
| Hard freeze (28°F) | Apr 27 · May 10 · May 24 | Sep 15 · Sep 28 · Oct 11 | 139 days | 100% |
Planting calendar for Ingomar
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 20 – Jun 26 |
| Tomatoes | Transplant outdoors | Jun 6 – May 30 |
| Peppers | Start seeds indoors | Apr 20 – May 21 |
| Peppers | Transplant outdoors | Jun 20 – Jul 21 |
| Eggplant | Start seeds indoors | May 7 – Jun 5 |
| Eggplant | Transplant outdoors | Jun 20 – Jul 21 |
| Cucumbers | Sow outdoors | Jun 20 – Jun 9 |
| Summer squash | Sow outdoors | Jun 6 – Jul 21 |
| Winter squash & pumpkins | Sow outdoors | Jun 20 – Jul 21 |
| Snap beans | Sow outdoors | Jun 6 – Jul 2 |
| Sweet corn | Sow outdoors | Jun 6 – May 30 |
| Watermelon & cantaloupe | Sow outdoors | Jun 20 – Jul 21 |
| Okra | Sow outdoors | Jun 13 – Jul 6 |
| Peas | Sow outdoors (spring) | Apr 20 – Jun 5 |
| Potatoes | Plant outdoors (spring) | Apr 20 – Jun 20 |
| Onions | Start seeds indoors (spring) | Mar 9 – Apr 5 |
| Onions | Transplant outdoors (spring) | May 7 – Jun 5 |
| Broccoli | Start seeds indoors (spring) | Apr 2 – May 6 |
| Broccoli | Transplant outdoors (spring) | May 7 – Jun 5 |
| Broccoli | Start seeds indoors (fall) | May 20 – May 30 |
| Broccoli | Transplant outdoors (fall) | Jun 19 – Jun 30 |
| Cabbage | Start seeds indoors (spring) | Mar 23 – Apr 20 |
| Cabbage | Transplant outdoors (spring) | Apr 20 – May 21 |
| Cabbage | Start seeds indoors (fall) | May 10 – Jun 9 |
| Cabbage | Transplant outdoors (fall) | Jun 9 – Jul 10 |
| Leaf lettuce | Sow outdoors (spring) | Apr 20 – Jul 6 |
| Leaf lettuce | Sow outdoors (fall) | Jun 9 – Jul 26 |
| Spinach | Sow outdoors (spring) | Apr 13 – May 27 |
| Spinach | Sow outdoors (fall) | Jun 26 – Jul 31 |
| Radishes | Sow outdoors (spring) | Apr 20 – Jun 10 |
| Radishes | Sow outdoors (fall) | Jun 9 – Aug 10 |
| Kale | Sow outdoors (spring) | May 7 – May 27 |
| Kale | Sow outdoors (fall) | Jun 2 – Jul 10 |
| Carrots | Sow outdoors (spring) | May 21 – Jul 6 |
| Carrots | Sow outdoors (fall) | May 10 – Jun 25 |
| Garlic | Plant outdoors (fall) | Sep 9 – Oct 10 |
Where these dates come from
ZIP code 59039 is matched to the NOAA station Ingomar 9 E, MT, 13.6 km away, at 2,800 ft elevation (219 ft lower than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Ingomar 9 E, MT (used) | 2,800 ft | May 21 | Sep 19 |
| Hysham, MT | 2,669 ft | May 10 | Sep 29 |
| Melstone, MT | 2,932 ft | May 10 | Sep 29 |
| Mosby 4 Ene, MT | 2,910 ft | May 5 | Oct 4 |
Frost dates near Ingomar
- Sumatra, MT 59083 · last May 10, first Sep 29
- Hysham, MT 59038 · last May 10, first Sep 29
- Melstone, MT 59054 · last May 10, first Sep 29
- Sanders, MT 59076 · last May 10, first Sep 29
- Mosby, MT 59058 · last May 5, first Oct 4
- Custer, MT 59024 · last May 10, first Sep 29
- Musselshell, MT 59059 · last May 10, first Sep 29
- Sand Springs, MT 59077 · last May 5, first Oct 4
Frequently asked questions
- When is the last frost in Ingomar, MT?
- For ZIP code 59039, the average last spring frost (32°F) is May 21, based on NOAA 1991-2020 climate normals for the Ingomar 9 E, MT weather station. There is a 1-in-10 chance of a frost after June 4.
- When is the first frost in Ingomar, MT?
- The average first fall frost (32°F) is September 19. There is a 1-in-10 chance of frost by September 6, so tender plants are at risk from that point on.
- How long is the growing season in 59039?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 120 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.