TODAY NOV22
TEMPERATURE40
HUMIDITY97
PRESSURE99150
WIND COND.270 29.5
  • 4737Fri20%70%
  • 5041Sat50%30%
  • 5137Sun
  • 5444Mon
  • 5736Tue40%
daynightWeather update from Islip, Long Island Mac Arthur Airport at
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Weather Quick Facts

  • The highest monthly average temperature in Port Jefferson for July is 75.9 degrees
  • The lowest monthly average temperature in Port Jefferson for January is 32.3 degrees
  • The most monthly precipitation in Port Jefferson occurs in August with 5.6 inches
  • The air quality index in Port Jefferson is 2% worse than the national average
  • The pollution index in Port Jefferson is 1338% worse than the national average

Compare Port Jefferson, NY Weather

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      Port Jefferson Average Temperature

      In the event that the weather data was unavailable for this city, estimates based upon nearby cities were used.
      MonthTemp. (min)Temp. (max)Temp. (avg)Precipitation
      January24°F41°F32°F4.0"
      February24°F43°F33°F3.0"
      March31°F50°F40°F4.2"
      April41°F61°F50°F3.5"
      May51°F71°F60°F3.6"
      June60°F79°F69°F4.7"
      July68°F85°F76°F3.1"
      August65°F83°F74°F5.6"
      September60°F78°F68°F3.1"
      October49°F67°F58°F4.1"
      November37°F56°F46°F3.0"
      December31°F47°F39°F4.9"

      Port Jefferson air quality index & pollution index

      In the event that the air quality/pollution data was unavailable for this city, estimates based upon nearby cities were used.
      IndexPort JeffersonNew YorkNational
      Air quality index434342
      Pollution index39,208,8006,179,2752,726,193

      Port Jefferson air quality

      MeasurementTotal
      Days measured365
      Days with good air quality262
      Days with moderate air quality82
      Days w/ poor A.Q. for sensitive groups18
      Days with unhealthy air quality3

      Air quality details

      PollutantTotal
      Arsenic0.060%
      Benzene0.320%
      Carbon Tetrachloride0.020%
      Lead0.320%
      Mercury0.130%

      Average monthly Port Jefferson temperature with heat index

      Port Jefferson monthly precipitation with daily maximum

      Port Jefferson monthly snow depth with daily maximum

      Port Jefferson monthly wind speed information

      Nearby cities with good air quality

      CityPopulationAir Quality IndexNational Avg.
      Calverton, NY5,2804118.0%
      Bayport, NY8,5844314.0%
      Brentwood, NY62,7434314.0%
      Holbrook, NY25,7944314.0%
      Ronkonkoma, NY18,9534314.0%
      Port Jefferson, NY8,0164314.0%

      Cities with similar population

      CityPopulationAir Quality IndexNational Avg.
      Franklin, VA8,0154020.0%
      Downingtown, PA8,0124216.0%
      Stone Mills, ON8,012n/a 
      Jefferson, WI8,0113726.0%
      Whitmore Lake, MI8,0104020.0%
      Port Jefferson, NY8,0164314.0%
      Source: The Port Jefferson, NY weather data displayed above is derived from the NOAA (National Oceanic and Atmospheric). Air quality and pollution data is derived from the EPA (United States Environmental Protection Agency). Air quality and pollution levels measured in a particular area may not be representative of the entire county.