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Monthly climate in Port Jefferson, New York, United States

Last updated: May 6, 2024

Under the Köppen–Geiger climate classification Port Jefferson features a humid subtropical climate (Cfa).Temperatures typically range between 2 °C (35 °F) and 24 °C (76 °F) through the year, but rarely can drop to -15 °C (6 °F) or can rise to as high as 33 °C (91 °F).The average annual precipitation amounts to about 1346 mm (53.0 inches) and receives 129 rainy days on the 1 mm (0.04 inches) threshold annually.Port Jefferson enjoys an average of 3001 hours of sunshine throughout the year, and daylight varies from 9 hours 16 minutes to 15 hours 3 minutes per day.

Monthly average temperatures in Port Jefferson, New York, United States §

The warmest months in Port Jefferson are July, August and September, with daily mean temperatures ranging from 21 to 24 °C (70 - 76 °F) throughout the day. The coldest temperatures usually occur in January, February and March, when daily mean temperatures range from 2 to 4 °C (35 - 40 °F) throughout the day. On average each year, Port Jefferson experiences 47 days above 25 °C (77.0 °F) and 46 days below 0 °C (32.0 °F).

Monthly average temperatures with daily means, minimums and maximums for period, average high and low temperatures in Port Jefferson, New York, 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 15°C
(60°F)		 15°C
(58°F)		 19°C
(67°F)		 22°C
(71°F)		 26°C
(79°F)		 29°C
(85°F)		 33°C
(91°F)		 31°C
(88°F)		 30°C
(87°F)		 29°C
(84°F)		 21°C
(70°F)		 17°C
(62°F)
Mean maximum 12°C
(54°F)		 12°C
(53°F)		 14°C
(58°F)		 17°C
(63°F)		 25°C
(77°F)		 28°C
(83°F)		 31°C
(87°F)		 30°C
(86°F)		 27°C
(82°F)		 24°C
(76°F)		 20°C
(68°F)		 15°C
(59°F)
Average high 4°C
(40°F)		 5°C
(41°F)		 7°C
(45°F)		 12°C
(53°F)		 17°C
(63°F)		 23°C
(73°F)		 26°C
(80°F)		 26°C
(79°F)		 23°C
(74°F)		 18°C
(65°F)		 12°C
(53°F)		 7°C
(44°F)
Daily mean 2°C
(35°F)		 2°C
(36°F)		 4°C
(40°F)		 9°C
(49°F)		 14°C
(58°F)		 20°C
(68°F)		 24°C
(76°F)		 24°C
(75°F)		 21°C
(70°F)		 16°C
(61°F)		 9°C
(49°F)		 5°C
(40°F)
Average low -1°C
(31°F)		 -0°C
(32°F)		 2°C
(36°F)		 7°C
(44°F)		 12°C
(54°F)		 18°C
(64°F)		 22°C
(72°F)		 22°C
(72°F)		 19°C
(66°F)		 14°C
(57°F)		 6°C
(44°F)		 2°C
(36°F)
Mean minimum -10°C
(14°F)		 -9°C
(16°F)		 -6°C
(22°F)		 2°C
(36°F)		 6°C
(44°F)		 13°C
(56°F)		 18°C
(64°F)		 18°C
(64°F)		 13°C
(56°F)		 7°C
(45°F)		 -2°C
(29°F)		 -5°C
(23°F)
Minimum -15°C
(6°F)		 -15°C
(6°F)		 -8°C
(17°F)		 -1°C
(31°F)		 3°C
(37°F)		 10°C
(50°F)		 16°C
(60°F)		 16°C
(61°F)		 11°C
(52°F)		 5°C
(41°F)		 -6°C
(21°F)		 -10°C
(15°F)

Compare climate in Port Jefferson with other places

Compare temperature, precipitation, sunshine, UV index in Port Jefferson, New York, United States with other places around the world.

Monthly average precipitation in Port Jefferson, New York, United States §

Port Jefferson usually has the most precipitation in April, October and December, with an average of 11 rainy days and 138 mm (5.4 inches) of precipitation per month.The driest months in Port Jefferson are January, June and September. On average, 87 mm (3.4 inches) of precipitation falls during these months.

Monthly average precipitation and precipitation days in Port Jefferson, New York, 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) 80 (3.1) 112 (4.4) 104 (4.1) 132 (5.2) 119 (4.7) 87 (3.4) 131 (5.2) 103 (4.0) 94 (3.7) 143 (5.6) 103 (4.0) 140 (5.5)
Average precipitation days (≥ 1 mm) 8 12 10 12 13 9 12 11 10 12 9 11

Monthly sunshine hours in Port Jefferson, New York, United States §

The sunniest months in Port Jefferson are June, July and August, when the sun shines an average of 10 hours 42 minutes a day.Least sunny months in Port Jefferson: January, February and December receive an average of 5 hours 36 minutes of sunshine daily.

Mean monthly sunshine duration, average sunshine hours per day and mean daily daylight hours in Port Jefferson, New York, 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 154 180 258 246 285 318 343 322 282 224 210 176
Mean daily daylight hours 9h 35m 10h 38m 11h 58m 13h 19m 14h 29m 15h 3m 14h 44m 13h 43m 12h 24m 11h 3m 9h 52m 9h 16m

Solar UV radiation in Port Jefferson, New York, United States §

Port Jefferson experiences the highest level of ultraviolet (UV) radiation in May, June and August, 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 4. For more detailed information, check out our hourly Port Jefferson UV Index data.

Average daily maximum UV levels by month for Port Jefferson, New York, 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) 3 5 6 8 10 10 9 9 8 6 4 2