Frost dates for 59872Superior, MT
The average last spring frost in Superior is May 17 and the average first fall frost is September 23, giving a typical growing season of about 125 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- May 17
- Average first fall frost
- Sep 23
- Growing season
- 125 days
Safer after Jun 8 (1-in-10 risk)
Possible by Sep 6 (1-in-10 risk)
Last frost typically in 202 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 20 · Jun 5 · Jul 3 | Aug 24 · Sep 9 · Sep 25 | 92 days | 100% |
| Frost / freeze (32°F) | May 1 · May 17 · Jun 8 | Sep 6 · Sep 23 · Oct 7 | 125 days | 100% |
| Hard freeze (28°F) | Apr 16 · May 1 · May 19 | Sep 20 · Oct 6 · Oct 24 | 157 days | 100% |
Planting calendar for Superior
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 16 – Jun 22 |
| Tomatoes | Transplant outdoors | Jun 2 – Jun 3 |
| Peppers | Start seeds indoors | Apr 16 – May 17 |
| Peppers | Transplant outdoors | Jun 16 – Jul 17 |
| Eggplant | Start seeds indoors | May 3 – Jun 1 |
| Eggplant | Transplant outdoors | Jun 16 – Jul 17 |
| Cucumbers | Sow outdoors | Jun 16 – Jun 13 |
| Summer squash | Sow outdoors | Jun 2 – Jul 17 |
| Winter squash & pumpkins | Sow outdoors | Jun 16 – Jul 17 |
| Snap beans | Sow outdoors | Jun 2 – Jul 6 |
| Sweet corn | Sow outdoors | Jun 2 – Jun 3 |
| Watermelon & cantaloupe | Sow outdoors | Jun 16 – Jul 17 |
| Okra | Sow outdoors | Jun 9 – Jul 2 |
| Peas | Sow outdoors (spring) | Apr 16 – Jun 1 |
| Potatoes | Plant outdoors (spring) | Apr 16 – Jun 16 |
| Onions | Start seeds indoors (spring) | Mar 5 – Apr 1 |
| Onions | Transplant outdoors (spring) | May 3 – Jun 1 |
| Broccoli | Start seeds indoors (spring) | Mar 29 – May 2 |
| Broccoli | Transplant outdoors (spring) | May 3 – Jun 1 |
| Broccoli | Start seeds indoors (fall) | May 24 – Jun 3 |
| Broccoli | Transplant outdoors (fall) | Jun 23 – Jul 4 |
| Cabbage | Start seeds indoors (spring) | Mar 19 – Apr 16 |
| Cabbage | Transplant outdoors (spring) | Apr 16 – May 17 |
| Cabbage | Start seeds indoors (fall) | May 14 – Jun 13 |
| Cabbage | Transplant outdoors (fall) | Jun 13 – Jul 14 |
| Leaf lettuce | Sow outdoors (spring) | Apr 16 – Jul 2 |
| Leaf lettuce | Sow outdoors (fall) | Jun 13 – Jul 30 |
| Spinach | Sow outdoors (spring) | Apr 9 – May 23 |
| Spinach | Sow outdoors (fall) | Jun 30 – Aug 4 |
| Radishes | Sow outdoors (spring) | Apr 16 – Jun 6 |
| Radishes | Sow outdoors (fall) | Jun 13 – Aug 14 |
| Kale | Sow outdoors (spring) | May 3 – May 23 |
| Kale | Sow outdoors (fall) | Jun 6 – Jul 14 |
| Carrots | Sow outdoors (spring) | May 17 – Jul 2 |
| Carrots | Sow outdoors (fall) | May 14 – Jun 29 |
| Garlic | Plant outdoors (fall) | Sep 13 – Oct 14 |
Where these dates come from
ZIP code 59872 is matched to the NOAA station Superior, MT, 2.3 km away, at 2,710 ft elevation (180 ft lower than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Superior, MT (used) | 2,710 ft | May 17 | Sep 23 |
| Saint Regis 1 Ne, MT | 2,660 ft | — | — |
| Alberton, MT | 3,060 ft | May 18 | Sep 25 |
| Haugan 1 W, MT | 3,160 ft | — | — |
Frost dates near Superior
- Paradise, MT 59856 · last —, first —
- Saint Regis, MT 59866 · last —, first —
- Plains, MT 59859 · last —, first —
- Alberton, MT 59820 · last May 18, first Sep 25
- Huson, MT 59846 · last May 18, first Sep 25
- De Borgia, MT 59830 · last —, first —
- Haugan, MT 59842 · last —, first —
- Dixon, MT 59831 · last May 12, first Oct 2
Frequently asked questions
- When is the last frost in Superior, MT?
- For ZIP code 59872, the average last spring frost (32°F) is May 17, based on NOAA 1991-2020 climate normals for the Superior, MT weather station. There is a 1-in-10 chance of a frost after June 8.
- When is the first frost in Superior, MT?
- The average first fall frost (32°F) is September 23. 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 59872?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 125 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.