Frost dates in Maine

NOAA 1991–2020 normals for a 32 °F freeze. Your own yard can run a little either side.

Short answer

Across 13 NOAA weather stations in Maine, the average last spring frost runs from April 26 at Portland Intl Jetport to May 27 at Houlton Intl Airport. The first fall frost comes as early as September 18 at Houlton Intl Airport and as late as October 16 at Augusta State Airport. Planting zones near these stations run from 4a to 6a.

Find yours by ZIP code

The table below is by weather station. For the station nearest you, and your planting zone, type your ZIP code.

Maine frost dates by weather station

Station	Last spring frost	First fall frost	Frost-free	Zone nearby
Augusta State Airport 350 ft	April 27 1 in 10 after May 7	October 16 1 in 10 by October 2	172 days	5b
Bangor Intl Airport 148 ft	May 4 1 in 10 after May 17	October 4 1 in 10 by September 23	153 days	5a
Brunswick NAS 70 ft	May 2 1 in 10 after May 14	October 10 1 in 10 by September 29	161 days	5b
Caribou Muni Airport 624 ft	May 7 1 in 10 after May 24	October 1 1 in 10 by September 17	147 days	4a
Frenchville Aroostook Airport 988 ft	May 6 1 in 10 after May 21	October 2 1 in 10 by September 18	149 days	4b
Fryeburg E Slopes Airport 445 ft	May 17 1 in 10 after June 1	September 25 1 in 10 by September 11	131 days	5a
Greenville Maine Forestry Svc 1,037 ft	May 7 1 in 10 after May 20	October 9 1 in 10 by September 27	155 days	4b
Houlton Intl Airport 476 ft	May 27 1 in 10 after June 10	September 18 1 in 10 by September 5	114 days	4b
Limestone 4 NNW 737 ft	May 16 1 in 10 after June 1	September 24 1 in 10 by September 12	131 days	4a
Millinocket Muni Airport 406 ft	May 8 1 in 10 after May 24	October 1 1 in 10 by September 19	146 days	5a
Old Town 2 W 127 ft	May 13 1 in 10 after May 28	September 28 1 in 10 by September 16	138 days	5a
Portland Intl Jetport 45 ft	April 26 1 in 10 after May 7	October 15 1 in 10 by October 2	172 days	6a
Wiscasset Airport 68 ft	May 8 1 in 10 after May 20	October 7 1 in 10 by September 24	152 days	5b

The average date is NOAA's 50% date: half of years have a later last frost, or an earlier first one. Plan by the 1-in-10 date if a freeze would cost you plants. Stations are NOAA's main weather stations, mostly airports. “Zone nearby” is the USDA 2023 zone of the nearest ZIP code within 10 miles. NOAA counts the frost season from August to July, so in the warmest places the “first fall” freeze lands after New Year.

How these dates work

Frost dates come from NOAA's 1991 to 2020 Climate Normals, which work out from each weather station's daily lows how likely the last spring freeze and the first fall freeze (32 °F) are by each date. We use the station nearest the middle of your ZIP code and show its height and distance, since a station on a hill or by a lake can differ from your yard.

The average date is the 50% date: half of years have a freeze after the spring date or before the fall one. The 1-in-10 dates are NOAA's 10% dates, the ones to plan by if a late freeze would cost you plants. Within one yard, cold air pools in low spots while walls and paving hold heat, so some corners freeze before others.

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