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Key findings

  • The highest monthly average temperature in Johnston for July is 77.4 degrees
  • The lowest monthly average temperature in Johnston for January is 23.5 degrees
  • The most monthly precipitation in Johnston occurs in June with 6.5 inches
  • The air quality index in Johnston is 22% better than the national average
  • The pollution index in Johnston is 84% worse than the national average

Compare Johnston, IA Weather

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      Johnston 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
      January14°F35°F23°F0.9"
      February17°F39°F26°F1.2"
      March30°F54°F41°F2.2"
      April41°F67°F53°F4.9"
      May51°F76°F63°F4.9"
      June62°F86°F74°F6.5"
      July66°F89°F77°F4.2"
      August64°F87°F75°F5.1"
      September56°F81°F68°F3.7"
      October43°F68°F55°F3.2"
      November31°F54°F42°F1.8"
      December18°F38°F27°F2.1"

      Johnston 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.
      IndexJohnstonIowaNational
      Air quality index393950
      Pollution index9,310,1601,643,8365,066,862

      Johnston air quality information

      MeasurementTotal
      Days measured365
      Days with good air quality306
      Days with moderate air quality59
      Days w/ poor A.Q. for sensitive groups0
      Days with unhealthy air quality0

      Johnston air quality information

      PollutantTotal
      Arsenic0.010%
      Benzene0.110%
      Carbon Tetrachloride0.080%
      Lead0.030%
      Mercury0.010%

      Average monthly Johnston temperature with heat index

      Johnston monthly precipitation with daily maximum

      Johnston monthly snow depth with daily maximum

      Johnston monthly wind speed information

      Nearby cities with good air quality

      City, StatePopulationAir Quality IndexNational Avg.
      Madrid, IA2,5853726%
      Alleman, IA4993726%
      Huxley, IA3,4743726%
      Woodward, IA1,6213726%
      Sheldahl, IA2493726%
      Johnston, IA19,4913922%

      Cities with similar population

      City, StatePopulationAir Quality IndexNational Avg.
      Payson, UT19,480468%
      Allendale, MI19,4753824%
      Sand Springs, OK19,5094510%
      Mead Valley, CA19,4688978%
      Langley Park, MD19,517476%
      Johnston, IA19,4913922%
      Source: The Johnston, IA 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.