Frost dates for 59032Grass Range, MT
The average last spring frost in Grass Range is May 20 and the average first fall frost is September 24, giving a typical growing season of about 126 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- May 20
- Average first fall frost
- Sep 24
- Growing season
- 126 days
Safer after Jun 6 (1-in-10 risk)
Possible by Sep 11 (1-in-10 risk)
Last frost typically in 198 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 19 · Jun 4 · Jul 1 | Aug 29 · Sep 13 · Sep 25 | 98 days | 100% |
| Frost / freeze (32°F) | May 6 · May 20 · Jun 6 | Sep 11 · Sep 24 · Oct 5 | 126 days | 100% |
| Hard freeze (28°F) | Apr 24 · May 6 · May 23 | Sep 21 · Oct 2 · Oct 17 | 149 days | 100% |
Planting calendar for Grass Range
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 19 – Jun 25 |
| Tomatoes | Transplant outdoors | Jun 5 – Jun 4 |
| Peppers | Start seeds indoors | Apr 19 – May 20 |
| Peppers | Transplant outdoors | Jun 19 – Jul 20 |
| Eggplant | Start seeds indoors | May 6 – Jun 4 |
| Eggplant | Transplant outdoors | Jun 19 – Jul 20 |
| Cucumbers | Sow outdoors | Jun 19 – Jun 14 |
| Summer squash | Sow outdoors | Jun 5 – Jul 20 |
| Winter squash & pumpkins | Sow outdoors | Jun 19 – Jul 20 |
| Snap beans | Sow outdoors | Jun 5 – Jul 7 |
| Sweet corn | Sow outdoors | Jun 5 – Jun 4 |
| Watermelon & cantaloupe | Sow outdoors | Jun 19 – Jul 20 |
| Okra | Sow outdoors | Jun 12 – Jul 5 |
| Peas | Sow outdoors (spring) | Apr 19 – Jun 4 |
| Potatoes | Plant outdoors (spring) | Apr 19 – Jun 19 |
| Onions | Start seeds indoors (spring) | Mar 8 – Apr 4 |
| Onions | Transplant outdoors (spring) | May 6 – Jun 4 |
| Broccoli | Start seeds indoors (spring) | Apr 1 – May 5 |
| Broccoli | Transplant outdoors (spring) | May 6 – Jun 4 |
| Broccoli | Start seeds indoors (fall) | May 25 – Jun 4 |
| Broccoli | Transplant outdoors (fall) | Jun 24 – Jul 5 |
| Cabbage | Start seeds indoors (spring) | Mar 22 – Apr 19 |
| Cabbage | Transplant outdoors (spring) | Apr 19 – May 20 |
| Cabbage | Start seeds indoors (fall) | May 15 – Jun 14 |
| Cabbage | Transplant outdoors (fall) | Jun 14 – Jul 15 |
| Leaf lettuce | Sow outdoors (spring) | Apr 19 – Jul 5 |
| Leaf lettuce | Sow outdoors (fall) | Jun 14 – Jul 31 |
| Spinach | Sow outdoors (spring) | Apr 12 – May 26 |
| Spinach | Sow outdoors (fall) | Jul 1 – Aug 5 |
| Radishes | Sow outdoors (spring) | Apr 19 – Jun 9 |
| Radishes | Sow outdoors (fall) | Jun 14 – Aug 15 |
| Kale | Sow outdoors (spring) | May 6 – May 26 |
| Kale | Sow outdoors (fall) | Jun 7 – Jul 15 |
| Carrots | Sow outdoors (spring) | May 20 – Jul 5 |
| Carrots | Sow outdoors (fall) | May 15 – Jun 30 |
| Garlic | Plant outdoors (fall) | Sep 14 – Oct 15 |
Where these dates come from
ZIP code 59032 is matched to the NOAA station Grass Range, MT, 1.8 km away, at 3,490 ft elevation (125 ft lower than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Grass Range, MT (used) | 3,490 ft | May 20 | Sep 24 |
| Lewistown 11Ese, MT | 5,028 ft | May 19 | Sep 25 |
| Flatwillow 4 Ene, MT | 3,292 ft | May 16 | Sep 28 |
| Valentine, MT | 2,905 ft | May 18 | Sep 21 |
Frost dates near Grass Range
- Teigen, MT 59084 · last May 20, first Sep 24
- Forest Grove, MT 59441 · last May 23, first Sep 21
- Roy, MT 59471 · last May 14, first Sep 24
- Winnett, MT 59087 · last May 16, first Sep 28
- Lewistown, MT 59457 · last May 23, first Sep 21
- Hilger, MT 59451 · last May 23, first Sep 21
- Moore, MT 59464 · last May 23, first Sep 21
- Roundup, MT 59073 · last May 20, first Sep 21
Frequently asked questions
- When is the last frost in Grass Range, MT?
- For ZIP code 59032, the average last spring frost (32°F) is May 20, based on NOAA 1991-2020 climate normals for the Grass Range, MT weather station. There is a 1-in-10 chance of a frost after June 6.
- When is the first frost in Grass Range, MT?
- The average first fall frost (32°F) is September 24. There is a 1-in-10 chance of frost by September 11, so tender plants are at risk from that point on.
- How long is the growing season in 59032?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 126 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.