Frost dates for Portland International Jetport, Maine
Half of years have their last spring frost by April 26, but 1 year in 10 still frosts after May 7.
A frost date is really a percentile from 30 years of records at a nearby weather station: in about half of years a frost still comes after the median date. Both numbers are below, so you can choose the risk yourself.
The odds
Last spring frost
How often a frost still comes on or after each date.
- 1 year in 10
- May 7
- 1 year in 5
- May 3
- 3 years in 10
- May 1
- 2 years in 5
- April 29
- Half of years (the median)
- April 26
First fall freeze
How often the first freeze comes on or before each date.
- 1 year in 10
- October 2
- 1 year in 5
- October 5
- 3 years in 10
- October 9
- 2 years in 5
- October 11
- Half of years (the median)
- October 15
- Growing season
- about 170 days
- Hardiness zones nearby
- 5b, 6a
- Summer days
- a usual high of about 25 °C77 °F
- Lettuce and spinach run to seed
- July to August, in hot, long days (how we know)
Summer and rain
A growing garden needs about 25 mm1 in of water a week, rain and watering together. Here is what a normal month brings.
Month by month
- January
- high ~0 °C32 °F · low ~-9 °C16 °F · rain ~89 mm3.5 in
- February
- high ~2 °C35 °F · low ~-8 °C17 °F · rain ~90 mm3.5 in
- March
- high ~6 °C42 °F · low ~-3 °C26 °F · rain ~104 mm4.1 in
- April
- high ~12 °C54 °F · low ~2 °C35 °F · rain ~112 mm4.4 in
- May
- high ~18 °C64 °F · low ~8 °C46 °F · rain ~93 mm3.7 in
- June
- high ~23 °C74 °F · low ~13 °C55 °F · rain ~105 mm4.1 in
- July
- high ~26 °C80 °F · low ~16 °C61 °F · rain ~87 mm3.4 in
- August
- high ~26 °C79 °F · low ~15 °C60 °F · rain ~91 mm3.6 in
- September
- high ~22 °C71 °F · low ~11 °C52 °F · rain ~96 mm3.8 in
- October
- high ~15 °C60 °F · low ~5 °C41 °F · rain ~133 mm5.2 in
- November
- high ~9 °C48 °F · low ~0 °C32 °F · rain ~108 mm4.2 in
- December
- high ~4 °C38 °F · low ~-5 °C22 °F · rain ~114 mm4.5 in
Where these numbers come from
NOAA NCEI 1991–2020 Climate Normals, the Portland International Jetport station (listed by NOAA as Portland Intl Jetport HCN, USW00014764), at 43.65, -70.30. These are that station’s own records, unshifted. The further your garden is from it, the less exactly they describe your ground. The planner finds the nearest station to your garden and lowers its confidence with distance, so no number is presented as if it were measured in your garden.
Cold air also pools in low ground on the clear, still nights when frost happens, so a hollow can freeze while a slope a few hundred feet away does not. No table can know that about your garden. A few seasons of your own logged frosts can.
ZIP codes nearest this station
04017, 04019, 04050, 04064, 04072, 04074, 04092, 04101, 04102, 04103, 04105, 04106…
+4 moreShow fewer
04107, 04108, 04109, 04110.
Nearby stations
The nearest stations and how their last-frost dates compare. Together they show how frost varies across your area.
- Hollis, ME, last frost by May 14
- Westport Island, ME, last frost by April 28
- Turner, ME, last frost by May 1
- E Sandwich, NH, last frost by May 6
- Epping, NH, last frost by May 7
- Beverly, MA, last frost by May 4
Other stations in Maine.
- Acadia NP, ME, last frost by April 27
When do I plant? · Where the dates come from
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