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Monthly climate in Portland, Maine, United States

Last updated: May 6, 2024

Under the Köppen–Geiger climate classification Portland features a humid continental climate (Dfb).Temperatures typically range between -2 °C (28 °F) and 20 °C (69 °F) through the year, but rarely can drop to -19 °C (-2 °F) or can rise to as high as 28 °C (83 °F).The average annual precipitation amounts to about 1327 mm (52.3 inches) and receives 124 rainy days on the 1 mm (0.04 inches) threshold annually.Portland enjoys an average of 2989 hours of sunshine throughout the year, and daylight varies from 8 hours 58 minutes to 15 hours 22 minutes per day.

Monthly average temperatures in Portland, Maine, United States §

The warmest months in Portland are July, August and September, with daily mean temperatures ranging from 17 to 20 °C (63 - 69 °F) throughout the day. The coldest temperatures usually occur in January, February and December, when daily mean temperatures range from -2 to 0 °C (28 - 33 °F) throughout the day. On average each year, Portland experiences 8 days above 25 °C (77.0 °F) and 91 days below 0 °C (32.0 °F).

Monthly average temperatures with daily means, minimums and maximums for period, average high and low temperatures in Portland, Maine, United States.Generated using Copernicus Climate Change Service information.Data for period from January 2017 to June 2022.
  Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Maximum 12°C
(54°F)		 14°C
(57°F)		 13°C
(56°F)		 18°C
(65°F)		 24°C
(76°F)		 28°C
(83°F)		 28°C
(83°F)		 28°C
(82°F)		 26°C
(79°F)		 21°C
(71°F)		 18°C
(64°F)		 13°C
(57°F)
Mean maximum 10°C
(50°F)		 10°C
(49°F)		 11°C
(52°F)		 14°C
(58°F)		 22°C
(71°F)		 24°C
(76°F)		 27°C
(81°F)		 27°C
(80°F)		 24°C
(76°F)		 20°C
(69°F)		 16°C
(62°F)		 12°C
(54°F)
Average high 1°C
(34°F)		 2°C
(36°F)		 4°C
(40°F)		 9°C
(48°F)		 14°C
(57°F)		 19°C
(66°F)		 22°C
(72°F)		 23°C
(73°F)		 20°C
(67°F)		 14°C
(58°F)		 8°C
(47°F)		 3°C
(38°F)
Daily mean -2°C
(28°F)		 -2°C
(29°F)		 1°C
(34°F)		 6°C
(43°F)		 11°C
(52°F)		 17°C
(62°F)		 20°C
(68°F)		 20°C
(69°F)		 17°C
(63°F)		 12°C
(54°F)		 5°C
(42°F)		 0°C
(33°F)
Average low -5°C
(22°F)		 -5°C
(24°F)		 -2°C
(29°F)		 4°C
(39°F)		 9°C
(48°F)		 14°C
(57°F)		 18°C
(64°F)		 18°C
(65°F)		 15°C
(59°F)		 10°C
(50°F)		 3°C
(37°F)		 -3°C
(28°F)
Mean minimum -16°C
(4°F)		 -15°C
(6°F)		 -12°C
(11°F)		 -1°C
(31°F)		 4°C
(40°F)		 10°C
(49°F)		 15°C
(59°F)		 14°C
(58°F)		 10°C
(50°F)		 4°C
(40°F)		 -6°C
(21°F)		 -12°C
(11°F)
Minimum -19°C
(-2°F)		 -17°C
(2°F)		 -15°C
(6°F)		 -3°C
(27°F)		 2°C
(36°F)		 8°C
(47°F)		 13°C
(56°F)		 14°C
(57°F)		 8°C
(46°F)		 1°C
(34°F)		 -12°C
(11°F)		 -18°C
(-1°F)

Compare climate in Portland with other places

Compare temperature, precipitation, sunshine, UV index in Portland, Maine, United States with other places around the world.

Monthly average precipitation in Portland, Maine, United States §

Portland usually has the most precipitation in April, October and December, with an average of 12 rainy days and 152 mm (6.0 inches) of precipitation per month.The driest months in Portland are June, August and September. On average, 77 mm (3.1 inches) of precipitation falls during these months.

Monthly average precipitation and precipitation days in Portland, Maine, United States.Generated using Copernicus Climate Change Service information.Data for period from January 2017 to January 2022.
  Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Average precipitation mm (inches) 97 (3.8) 103 (4.1) 91 (3.6) 149 (5.9) 94 (3.7) 80 (3.2) 123 (4.9) 75 (3.0) 77 (3.0) 163 (6.4) 130 (5.1) 144 (5.7)
Average precipitation days (≥ 1 mm) 9 10 9 13 10 9 12 9 8 13 12 10

Monthly sunshine hours in Portland, Maine, United States §

The sunniest months in Portland are June, July and August, when the sun shines an average of 10 hours 50 minutes a day.Least sunny months in Portland: January, February and December receive an average of 5 hours 32 minutes of sunshine daily.

Mean monthly sunshine duration, average sunshine hours per day and mean daily daylight hours in Portland, Maine, United States.Generated using Copernicus Atmosphere Monitoring Service information.Data for period from January 2017 to January 2022.
  Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Mean monthly sunshine hours 147 182 255 243 294 329 332 335 287 216 190 173
Mean daily daylight hours 9h 20m 10h 30m 11h 58m 13h 27m 14h 43m 15h 22m 15h 1m 13h 53m 12h 26m 10h 57m 9h 38m 8h 58m

Solar UV radiation in Portland, Maine, United States §

Portland experiences the highest level of ultraviolet (UV) radiation in May, June and July, when the maximum UV index can reach values of 9 - 10, which corresponds to the Very High category of sun exposure.January, November and December are in the Low / Moderate exposure category. In these months, the maximum values of the UV index do not exceed 3. For more detailed information, check out our hourly Portland UV Index data.

Average daily maximum UV levels by month for Portland, Maine, United States.Generated using Copernicus Atmosphere Monitoring Service information.Data for period from January 2022 to January 2023.
  Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
UV Index (month maximum) 2 4 5 7 9 10 9 8 7 5 3 2