Frost dates for 58274Portland, ND
The average last spring frost in Portland is May 13 and the average first fall frost is September 27, giving a typical growing season of about 136 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- May 13
- Average first fall frost
- Sep 27
- Growing season
- 136 days
Safer after May 25 (1-in-10 risk)
Possible by Sep 14 (1-in-10 risk)
Last frost typically in 199 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 11 · May 23 · Jun 2 | Sep 4 · Sep 17 · Sep 28 | 117 days | 100% |
| Frost / freeze (32°F) | Apr 30 · May 13 · May 25 | Sep 14 · Sep 27 · Oct 9 | 136 days | 100% |
| Hard freeze (28°F) | Apr 20 · May 4 · May 17 | Sep 24 · Oct 6 · Oct 19 | 154 days | 100% |
Planting calendar for Portland
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 7 |
| 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 17 |
| Summer squash | Sow outdoors | May 29 – Jul 13 |
| Winter squash & pumpkins | Sow outdoors | Jun 12 – Jul 13 |
| Snap beans | Sow outdoors | May 29 – Jul 10 |
| Sweet corn | Sow outdoors | May 29 – Jun 7 |
| 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 28 – Jun 7 |
| Broccoli | Transplant outdoors (fall) | Jun 27 – Jul 8 |
| Cabbage | Start seeds indoors (spring) | Mar 15 – Apr 12 |
| Cabbage | Transplant outdoors (spring) | Apr 12 – May 13 |
| Cabbage | Start seeds indoors (fall) | May 18 – Jun 17 |
| Cabbage | Transplant outdoors (fall) | Jun 17 – Jul 18 |
| Leaf lettuce | Sow outdoors (spring) | Apr 12 – Jun 28 |
| Leaf lettuce | Sow outdoors (fall) | Jun 17 – Aug 3 |
| Spinach | Sow outdoors (spring) | Apr 5 – May 19 |
| Spinach | Sow outdoors (fall) | Jul 4 – Aug 8 |
| Radishes | Sow outdoors (spring) | Apr 12 – Jun 2 |
| Radishes | Sow outdoors (fall) | Jun 17 – Aug 18 |
| Kale | Sow outdoors (spring) | Apr 29 – May 19 |
| Kale | Sow outdoors (fall) | Jun 10 – Jul 18 |
| Carrots | Sow outdoors (spring) | May 13 – Jun 28 |
| Carrots | Sow outdoors (fall) | May 18 – Jul 3 |
| Garlic | Plant outdoors (fall) | Sep 17 – Oct 18 |
Where these dates come from
ZIP code 58274 is matched to the NOAA station Mayville, ND, 2.5 km away, at 983 ft elevation (11 ft lower than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Mayville, ND (used) | 983 ft | May 13 | Sep 27 |
| Hillsboro 3 N, ND | 910 ft | May 2 | Oct 9 |
| Colgate, ND | 1,180 ft | May 10 | Sep 24 |
| Larimore 4Sw, ND | 1,152 ft | May 11 | Sep 28 |
Frost dates near Portland
- Mayville, ND 58257 · last May 13, first Sep 27
- Hatton, ND 58240 · last May 13, first Sep 27
- Clifford, ND 58016 · last May 13, first Sep 27
- Blanchard, ND 58009 · last May 2, first Oct 9
- Buxton, ND 58218 · last May 2, first Oct 9
- Galesburg, ND 58035 · last May 10, first Sep 24
- Reynolds, ND 58275 · last May 13, first Sep 27
- Finley, ND 58230 · last May 17, first Sep 23
Frequently asked questions
- When is the last frost in Portland, ND?
- For ZIP code 58274, the average last spring frost (32°F) is May 13, based on NOAA 1991-2020 climate normals for the Mayville, ND weather station. There is a 1-in-10 chance of a frost after May 25.
- When is the first frost in Portland, ND?
- The average first fall frost (32°F) is September 27. 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 58274?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 136 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.