Frost dates for 04101Portland, ME
The average last spring frost in Portland is April 26 and the average first fall frost is October 15, giving a typical growing season of about 170 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- Apr 26
- Average first fall frost
- Oct 15
- Growing season
- 170 days
Safer after May 7 (1-in-10 risk)
Possible by Oct 2 (1-in-10 risk)
Last frost typically in 176 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 28 · May 7 · May 20 | Sep 24 · Oct 4 · Oct 17 | 149 days | 100% |
| Frost / freeze (32°F) | Apr 16 · Apr 26 · May 7 | Oct 2 · Oct 15 · Oct 30 | 170 days | 100% |
| Hard freeze (28°F) | Apr 3 · Apr 14 · Apr 25 | Oct 14 · Oct 27 · Nov 9 | 195 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 | Mar 26 – Jun 1 |
| Tomatoes | Transplant outdoors | May 12 – Jun 25 |
| Peppers | Start seeds indoors | Mar 26 – Apr 26 |
| Peppers | Transplant outdoors | May 26 – Jun 26 |
| Eggplant | Start seeds indoors | Apr 12 – May 11 |
| Eggplant | Transplant outdoors | May 26 – Jun 26 |
| Cucumbers | Sow outdoors | May 26 – Jul 5 |
| Summer squash | Sow outdoors | May 12 – Jun 26 |
| Winter squash & pumpkins | Sow outdoors | May 26 – Jun 26 |
| Snap beans | Sow outdoors | May 12 – Jul 28 |
| Sweet corn | Sow outdoors | May 12 – Jun 25 |
| Watermelon & cantaloupe | Sow outdoors | May 26 – Jun 26 |
| Okra | Sow outdoors | May 19 – Jun 11 |
| Peas | Sow outdoors (spring) | Mar 26 – May 11 |
| Potatoes | Plant outdoors (spring) | Mar 26 – May 26 |
| Onions | Start seeds indoors (spring) | Feb 12 – Mar 11 |
| Onions | Transplant outdoors (spring) | Apr 12 – May 11 |
| Broccoli | Start seeds indoors (spring) | Mar 8 – Apr 11 |
| Broccoli | Transplant outdoors (spring) | Apr 12 – May 11 |
| Broccoli | Start seeds indoors (fall) | Jun 15 – Jun 25 |
| Broccoli | Transplant outdoors (fall) | Jul 15 – Jul 26 |
| Cabbage | Start seeds indoors (spring) | Feb 26 – Mar 26 |
| Cabbage | Transplant outdoors (spring) | Mar 26 – Apr 26 |
| Cabbage | Start seeds indoors (fall) | Jun 5 – Jul 5 |
| Cabbage | Transplant outdoors (fall) | Jul 5 – Aug 5 |
| Leaf lettuce | Sow outdoors (spring) | Mar 26 – Jun 11 |
| Leaf lettuce | Sow outdoors (fall) | Jul 5 – Aug 21 |
| Spinach | Sow outdoors (spring) | Mar 19 – May 2 |
| Spinach | Sow outdoors (fall) | Jul 22 – Aug 26 |
| Radishes | Sow outdoors (spring) | Mar 26 – May 16 |
| Radishes | Sow outdoors (fall) | Jul 5 – Sep 5 |
| Kale | Sow outdoors (spring) | Apr 12 – May 2 |
| Kale | Sow outdoors (fall) | Jun 28 – Aug 5 |
| Carrots | Sow outdoors (spring) | Apr 26 – Jun 11 |
| Carrots | Sow outdoors (fall) | Jun 5 – Jul 21 |
| Garlic | Plant outdoors (fall) | Oct 5 – Nov 5 |
Where these dates come from
ZIP code 04101 is matched to the NOAA station Portland Intl Jetport, ME, 3.5 km away, at 45 ft elevation (12 ft higher than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Portland Intl Jetport, ME (used) | 45 ft | Apr 26 | Oct 15 |
| Gray, ME | 378 ft | Apr 28 | Oct 19 |
| Windham 2Nw, ME | 443 ft | Apr 30 | Oct 20 |
| West Buxton 2 Nnw, ME | 220 ft | May 7 | Oct 4 |
Frost dates near Portland
- Portland, ME 04104 · last Apr 26, first Oct 15
- South Portland, ME 04116 · last Apr 26, first Oct 15
- Peaks Island, ME 04108 · last Apr 26, first Oct 15
- Cape Elizabeth, ME 04107 · last Apr 26, first Oct 15
- Falmouth, ME 04105 · last Apr 26, first Oct 15
- Westbrook, ME 04092 · last Apr 26, first Oct 15
- Long Island, ME 04050 · last Apr 26, first Oct 15
- Scarborough, ME 04070 · last Apr 26, first Oct 15
Frequently asked questions
- When is the last frost in Portland, ME?
- For ZIP code 04101, the average last spring frost (32°F) is April 26, based on NOAA 1991-2020 climate normals for the Portland Intl Jetport, ME weather station. There is a 1-in-10 chance of a frost after May 7.
- When is the first frost in Portland, ME?
- The average first fall frost (32°F) is October 15. There is a 1-in-10 chance of frost by October 2, so tender plants are at risk from that point on.
- How long is the growing season in 04101?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 170 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.