Frost dates for 59641Radersburg, MT
The average last spring frost in Radersburg is May 19 and the average first fall frost is September 19, giving a typical growing season of about 122 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- May 19
- Average first fall frost
- Sep 19
- Growing season
- 122 days
Safer after Jun 2 (1-in-10 risk)
Possible by Sep 5 (1-in-10 risk)
Last frost typically in 204 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 22 · Jun 5 · Jun 23 | Aug 25 · Sep 7 · Sep 21 | 92 days | 100% |
| Frost / freeze (32°F) | May 8 · May 19 · Jun 2 | Sep 5 · Sep 19 · Oct 2 | 122 days | 100% |
| Hard freeze (28°F) | Apr 26 · May 7 · May 20 | Sep 17 · Oct 1 · Oct 14 | 145 days | 100% |
Planting calendar for Radersburg
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 – May 30 |
| 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 9 |
| Summer squash | Sow outdoors | Jun 4 – Jul 19 |
| Winter squash & pumpkins | Sow outdoors | Jun 18 – Jul 19 |
| Snap beans | Sow outdoors | Jun 4 – Jul 2 |
| Sweet corn | Sow outdoors | Jun 4 – May 30 |
| 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 20 – May 30 |
| Broccoli | Transplant outdoors (fall) | Jun 19 – Jun 30 |
| Cabbage | Start seeds indoors (spring) | Mar 21 – Apr 18 |
| Cabbage | Transplant outdoors (spring) | Apr 18 – May 19 |
| Cabbage | Start seeds indoors (fall) | May 10 – Jun 9 |
| Cabbage | Transplant outdoors (fall) | Jun 9 – Jul 10 |
| Leaf lettuce | Sow outdoors (spring) | Apr 18 – Jul 4 |
| Leaf lettuce | Sow outdoors (fall) | Jun 9 – Jul 26 |
| Spinach | Sow outdoors (spring) | Apr 11 – May 25 |
| Spinach | Sow outdoors (fall) | Jun 26 – Jul 31 |
| Radishes | Sow outdoors (spring) | Apr 18 – Jun 8 |
| Radishes | Sow outdoors (fall) | Jun 9 – Aug 10 |
| Kale | Sow outdoors (spring) | May 5 – May 25 |
| Kale | Sow outdoors (fall) | Jun 2 – Jul 10 |
| Carrots | Sow outdoors (spring) | May 19 – Jul 4 |
| Carrots | Sow outdoors (fall) | May 10 – Jun 25 |
| Garlic | Plant outdoors (fall) | Sep 9 – Oct 10 |
Where these dates come from
ZIP code 59641 is matched to the NOAA station Townsend 3Se, MT, 17.3 km away, at 3,964 ft elevation (387 ft lower than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Townsend 3Se, MT (used) | 3,964 ft | May 19 | Sep 19 |
| Trident, MT | 4,036 ft | May 9 | Sep 27 |
| Tizer Gardens, MT | 4,672 ft | Jun 18 | Sep 5 |
| Boulder, MT | 4,904 ft | Jun 7 | Sep 8 |
Frost dates near Radersburg
- Toston, MT 59643 · last May 19, first Sep 19
- Townsend, MT 59644 · last May 19, first Sep 19
- Winston, MT 59647 · last May 19, first Sep 19
- Jefferson City, MT 59638 · last Jun 7, first Sep 8
- Cardwell, MT 59721 · last Apr 30, first Oct 10
- Three Forks, MT 59752 · last May 9, first Sep 27
- Boulder, MT 59632 · last Jun 7, first Sep 8
- Clancy, MT 59634 · last May 9, first Sep 30
Frequently asked questions
- When is the last frost in Radersburg, MT?
- For ZIP code 59641, the average last spring frost (32°F) is May 19, based on NOAA 1991-2020 climate normals for the Townsend 3Se, MT weather station. There is a 1-in-10 chance of a frost after June 2.
- When is the first frost in Radersburg, MT?
- The average first fall frost (32°F) is September 19. There is a 1-in-10 chance of frost by September 5, so tender plants are at risk from that point on.
- How long is the growing season in 59641?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 122 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.