Last spring frost
May 11
Frost Dates for Winthrop, ME
First fall frost
Sep 29
Growing season
138 days
Hardiness zone
5b
In an average year around Winthrop, ME, the last spring frost (32°F) is about May 11 and the first fall frost is about Sep 29, giving roughly a 138-day growing season. To be safe most years, wait until Apr 29 before setting out tender plants.
Last spring frost
Dates the last frost of spring typically ends. Plant tender crops after the risk has passed for your comfort level.
| Frost intensity | Early (10%) | Average (50%) | Late (90%) |
|---|---|---|---|
| Light (36°F) | Jun 6 | May 23 | May 10 |
| Freeze (32°F) | May 24 | May 11 | Apr 29 |
| Hard (28°F) | May 12 | Apr 30 | Apr 18 |
| Severe (24°F) | Apr 29 | Apr 17 | Apr 5 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Jun 6 | Jun 1 | May 29 | May 26 | May 23 | May 21 | May 18 | May 15 | May 10 |
| 32°F | May 24 | May 19 | May 16 | May 13 | May 11 | May 8 | May 6 | May 2 | Apr 29 |
| 28°F | May 12 | May 7 | May 3 | May 1 | Apr 30 | Apr 27 | Apr 25 | Apr 22 | Apr 18 |
| 24°F | Apr 29 | Apr 25 | Apr 21 | Apr 19 | Apr 17 | Apr 14 | Apr 11 | Apr 8 | Apr 5 |
| 20°F | Apr 17 | Apr 13 | Apr 10 | Apr 7 | Apr 6 | Apr 4 | Apr 3 | Mar 31 | Mar 26 |
| 16°F | Apr 8 | Apr 5 | Apr 3 | Apr 1 | Mar 31 | Mar 28 | Mar 25 | Mar 21 | Mar 17 |
First fall frost
Dates the first frost of fall typically arrives. Count back by a crop's days-to-maturity to know your planting cutoff.
| Frost intensity | Early (10%) | Average (50%) | Late (90%) |
|---|---|---|---|
| Light (36°F) | Sep 7 | Sep 19 | Sep 30 |
| Freeze (32°F) | Sep 16 | Sep 29 | Oct 11 |
| Hard (28°F) | Sep 26 | Oct 8 | Oct 26 |
| Severe (24°F) | Oct 7 | Oct 23 | Nov 6 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Sep 7 | Sep 11 | Sep 14 | Sep 16 | Sep 19 | Sep 21 | Sep 24 | Sep 26 | Sep 30 |
| 32°F | Sep 16 | Sep 20 | Sep 23 | Sep 26 | Sep 29 | Oct 1 | Oct 3 | Oct 6 | Oct 11 |
| 28°F | Sep 26 | Oct 1 | Oct 3 | Oct 6 | Oct 8 | Oct 12 | Oct 16 | Oct 20 | Oct 26 |
| 24°F | Oct 7 | Oct 11 | Oct 16 | Oct 20 | Oct 23 | Oct 26 | Oct 30 | Nov 2 | Nov 6 |
| 20°F | Oct 20 | Oct 26 | Oct 30 | Nov 1 | Nov 4 | Nov 7 | Nov 9 | Nov 12 | Nov 17 |
| 16°F | Nov 3 | Nov 7 | Nov 11 | Nov 13 | Nov 16 | Nov 18 | Nov 20 | Nov 23 | Nov 27 |
Growing season is measured at 32°F with about 50% probability. Hardiness zone from the 2023 USDA map; frost normals from NOAA 1991-2020.
Where this data comes from
@endif These dates are computed from the nearest official weather station with long-term records: Livermore Falls 1 E, Me, about 10.7 miles away@if(!empty($station['elevation_ft'])), at 380 ft elevation. The further the station and the greater the elevation difference from your yard, the more your local frost timing can vary.
How we calculate these dates
Frost and freeze dates come from the NOAA 1991–2020 U.S. Climate Normals, the National Oceanic and Atmospheric Administration's 30-year averages for each weather station. A date shown at the 50% level is the median: in half of years the frost falls on or before it. The 10% and 90% columns show the early and late ends of the range, so you can plant on the odds you're comfortable with. These are long-term averages, not a forecast for this year - always check your local outlook before planting.
Source: NOAA National Centers for Environmental Information, 1991–2020 Climate Normals (public domain). Harman is not affiliated with or endorsed by NOAA.
Frequently asked questions
When is the last frost in Winthrop, ME?
On average, the last spring frost (32°F) around Winthrop, ME is about May 11. In cooler years it can run later, so for a safer bet many gardeners wait until Apr 29.
When is the first frost in the fall?
The first fall frost around Winthrop, ME typically arrives about Sep 29. Count back by a crop's days to maturity to find the latest date you can plant it.
When can I plant tomatoes and other tender crops?
Tender crops like tomatoes, peppers and basil are damaged by frost, so wait until the last spring frost has passed - around May 11 on average, or Apr 29 to be safe most years.
How long is the growing season here?
The frost-free growing season (between the last spring and first fall 32°F frost) is about 138 days in a typical year.
Are these dates a forecast for this year?
No. They are 30-year averages from the NOAA 1991–2020 Climate Normals, not a prediction for the current year. Use them for planning and always check your local weather forecast before planting or protecting crops.
Local weather for 04284 Planting calendar → Maine frost dates →
Data source: NOAA 1991–2020 Climate Normals · Page updated Aug 4, 2026