Frost dates for 59721Cardwell, MT
The average last spring frost in Cardwell is April 30 and the average first fall frost is October 10, giving a typical growing season of about 162 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- Apr 30
- Average first fall frost
- Oct 10
- Growing season
- 162 days
Safer after May 14 (1-in-10 risk)
Possible by Sep 27 (1-in-10 risk)
Last frost typically in 185 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) | Apr 30 · May 15 · Jun 2 | Sep 17 · Sep 30 · Oct 13 | 136 days | 100% |
| Frost / freeze (32°F) | Apr 15 · Apr 30 · May 14 | Sep 27 · Oct 10 · Oct 27 | 162 days | 100% |
| Hard freeze (28°F) | Apr 1 · Apr 17 · May 5 | Oct 4 · Oct 22 · Nov 7 | 188 days | 100% |
Planting calendar for Cardwell
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 | Mar 30 – Jun 5 |
| Tomatoes | Transplant outdoors | May 16 – Jun 20 |
| Peppers | Start seeds indoors | Mar 30 – Apr 30 |
| Peppers | Transplant outdoors | May 30 – Jun 30 |
| Eggplant | Start seeds indoors | Apr 16 – May 15 |
| Eggplant | Transplant outdoors | May 30 – Jun 30 |
| Cucumbers | Sow outdoors | May 30 – Jun 30 |
| Summer squash | Sow outdoors | May 16 – Jun 30 |
| Winter squash & pumpkins | Sow outdoors | May 30 – Jun 30 |
| Snap beans | Sow outdoors | May 16 – Jul 23 |
| Sweet corn | Sow outdoors | May 16 – Jun 20 |
| Watermelon & cantaloupe | Sow outdoors | May 30 – Jun 30 |
| Okra | Sow outdoors | May 23 – Jun 15 |
| Peas | Sow outdoors (spring) | Mar 30 – May 15 |
| Potatoes | Plant outdoors (spring) | Mar 30 – May 30 |
| Onions | Start seeds indoors (spring) | Feb 16 – Mar 15 |
| Onions | Transplant outdoors (spring) | Apr 16 – May 15 |
| Broccoli | Start seeds indoors (spring) | Mar 12 – Apr 15 |
| Broccoli | Transplant outdoors (spring) | Apr 16 – May 15 |
| Broccoli | Start seeds indoors (fall) | Jun 10 – Jun 20 |
| Broccoli | Transplant outdoors (fall) | Jul 10 – Jul 21 |
| Cabbage | Start seeds indoors (spring) | Mar 2 – Mar 30 |
| Cabbage | Transplant outdoors (spring) | Mar 30 – Apr 30 |
| Cabbage | Start seeds indoors (fall) | May 31 – Jun 30 |
| Cabbage | Transplant outdoors (fall) | Jun 30 – Jul 31 |
| Leaf lettuce | Sow outdoors (spring) | Mar 30 – Jun 15 |
| Leaf lettuce | Sow outdoors (fall) | Jun 30 – Aug 16 |
| Spinach | Sow outdoors (spring) | Mar 23 – May 6 |
| Spinach | Sow outdoors (fall) | Jul 17 – Aug 21 |
| Radishes | Sow outdoors (spring) | Mar 30 – May 20 |
| Radishes | Sow outdoors (fall) | Jun 30 – Aug 31 |
| Kale | Sow outdoors (spring) | Apr 16 – May 6 |
| Kale | Sow outdoors (fall) | Jun 23 – Jul 31 |
| Carrots | Sow outdoors (spring) | Apr 30 – Jun 15 |
| Carrots | Sow outdoors (fall) | May 31 – Jul 16 |
| Garlic | Plant outdoors (fall) | Sep 30 – Oct 31 |
Where these dates come from
ZIP code 59721 is matched to the NOAA station Norris Madison Pwr House, MT, 46.6 km away, at 4,745 ft elevation (34 ft higher than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Norris Madison Pwr House, MT (used) | 4,745 ft | Apr 30 | Oct 10 |
| Trident, MT | 4,036 ft | May 9 | Sep 27 |
| Logan Landfill, MT | 4,243 ft | May 26 | Sep 15 |
| Boulder, MT | 4,904 ft | Jun 7 | Sep 8 |
Frost dates near Cardwell
- Willow Creek, MT 59760 · last May 9, first Sep 27
- Harrison, MT 59735 · last Apr 30, first Oct 10
- Three Forks, MT 59752 · last May 9, first Sep 27
- Whitehall, MT 59759 · last Jun 8, first Sep 2
- Pony, MT 59747 · last Jun 4, first Sep 18
- Toston, MT 59643 · last May 19, first Sep 19
- Radersburg, MT 59641 · last May 19, first Sep 19
- Manhattan, MT 59741 · last May 26, first Sep 16
Frequently asked questions
- When is the last frost in Cardwell, MT?
- For ZIP code 59721, the average last spring frost (32°F) is April 30, based on NOAA 1991-2020 climate normals for the Norris Madison Pwr House, MT weather station. There is a 1-in-10 chance of a frost after May 14.
- When is the first frost in Cardwell, MT?
- The average first fall frost (32°F) is October 10. There is a 1-in-10 chance of frost by September 27, so tender plants are at risk from that point on.
- How long is the growing season in 59721?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 162 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.