Frost dates for 59034Hardin, MT
The average last spring frost in Hardin is May 13 and the average first fall frost is September 29, 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 29
- Growing season
- 135 days
Safer after May 26 (1-in-10 risk)
Possible by Sep 14 (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 13 · May 25 · Jun 9 | Sep 3 · Sep 18 · Oct 1 | 114 days | 100% |
| Frost / freeze (32°F) | Apr 30 · May 13 · May 26 | Sep 14 · Sep 29 · Oct 10 | 135 days | 100% |
| Hard freeze (28°F) | Apr 16 · May 1 · May 13 | Sep 24 · Oct 7 · Oct 20 | 158 days | 100% |
Planting calendar for Hardin
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 9 |
| 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 19 |
| Summer squash | Sow outdoors | May 29 – Jul 13 |
| Winter squash & pumpkins | Sow outdoors | Jun 12 – Jul 13 |
| Snap beans | Sow outdoors | May 29 – Jul 12 |
| Sweet corn | Sow outdoors | May 29 – Jun 9 |
| 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 30 – Jun 9 |
| Broccoli | Transplant outdoors (fall) | Jun 29 – Jul 10 |
| Cabbage | Start seeds indoors (spring) | Mar 15 – Apr 12 |
| Cabbage | Transplant outdoors (spring) | Apr 12 – May 13 |
| Cabbage | Start seeds indoors (fall) | May 20 – Jun 19 |
| Cabbage | Transplant outdoors (fall) | Jun 19 – Jul 20 |
| Leaf lettuce | Sow outdoors (spring) | Apr 12 – Jun 28 |
| Leaf lettuce | Sow outdoors (fall) | Jun 19 – Aug 5 |
| Spinach | Sow outdoors (spring) | Apr 5 – May 19 |
| Spinach | Sow outdoors (fall) | Jul 6 – Aug 10 |
| Radishes | Sow outdoors (spring) | Apr 12 – Jun 2 |
| Radishes | Sow outdoors (fall) | Jun 19 – Aug 20 |
| Kale | Sow outdoors (spring) | Apr 29 – May 19 |
| Kale | Sow outdoors (fall) | Jun 12 – Jul 20 |
| Carrots | Sow outdoors (spring) | May 13 – Jun 28 |
| Carrots | Sow outdoors (fall) | May 20 – Jul 5 |
| Garlic | Plant outdoors (fall) | Sep 19 – Oct 20 |
Where these dates come from
ZIP code 59034 is matched to the NOAA station Hardin, MT, 2 km away, at 2,880 ft elevation (10 ft lower than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Hardin, MT (used) | 2,880 ft | May 13 | Sep 29 |
| Hysham 25 Sse, MT | 3,100 ft | May 26 | Sep 16 |
| Huntley Exp Stn, MT | 3,034 ft | May 12 | Sep 25 |
| Yellowtail Dam, MT | 3,305 ft | May 7 | Oct 5 |
Frost dates near Hardin
- Crow Agency, MT 59022 · last May 13, first Sep 29
- Garryowen, MT 59031 · last May 7, first Oct 5
- Pompeys Pillar, MT 59064 · last May 12, first Sep 25
- Bighorn, MT 59010 · last May 26, first Sep 16
- Custer, MT 59024 · last May 10, first Sep 29
- Saint Xavier, MT 59075 · last May 7, first Oct 5
- Ballantine, MT 59006 · last May 12, first Sep 25
- Worden, MT 59088 · last May 12, first Sep 25
Frequently asked questions
- When is the last frost in Hardin, MT?
- For ZIP code 59034, the average last spring frost (32°F) is May 13, based on NOAA 1991-2020 climate normals for the Hardin, MT weather station. There is a 1-in-10 chance of a frost after May 26.
- When is the first frost in Hardin, MT?
- The average first fall frost (32°F) is September 29. 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 59034?
- 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.