TODAY APR16
TEMPERATURE26
HUMIDITY92
PRESSURE30.12
WIND COND.
  • 3925Fri30%20%
  • 4730Sat
  • 5726Sun50%
  • 3721Mon
  • 4324Tue
daynightWeather update from Custer, Custer County Airport at

Key findings

  • The highest monthly average temperature in Keystone for July is 67.4 degrees
  • The lowest monthly average temperature in Keystone for December is 23.4 degrees
  • The most monthly precipitation in Keystone occurs in May with 3.3 inches
  • The air quality index in Keystone is 12% better than the national average
  • The pollution index in Keystone is 61% better than the national average

Compare Keystone, SD Weather

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      Keystone 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
      January15°F37°F25°F0.4"
      February14°F36°F24°F0.6"
      March23°F48°F34°F1.0"
      April28°F53°F39°F2.4"
      May37°F61°F48°F3.3"
      June47°F74°F60°F2.9"
      July53°F82°F67°F2.7"
      August51°F80°F65°F2.4"
      September43°F72°F56°F1.7"
      October32°F57°F43°F1.3"
      November23°F46°F34°F0.6"
      December13°F35°F23°F0.7"

      Keystone 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.
      IndexKeystoneSouth DakotaNational
      Air quality index443650
      Pollution index1,968,790463,9835,066,862

      Keystone air quality information

      MeasurementTotal
      Days measured365
      Days with good air quality274
      Days with moderate air quality87
      Days w/ poor A.Q. for sensitive groups4
      Days with unhealthy air quality0

      Keystone air quality information

      PollutantTotal
      Arsenic0.003%
      Benzene0.030%
      Carbon Tetrachloride0.004%
      Lead0.020%
      Mercury0.010%

      Average monthly Keystone temperature with heat index

      Keystone monthly precipitation with daily maximum

      Keystone monthly snow depth with daily maximum

      Keystone monthly wind speed information

      Nearby cities with good air quality

      City, StatePopulationAir Quality IndexNational Avg.
      Hill City, SD1,3584412%
      Colonial Pine Hills, SD2,0694412%
      Johnson Siding, SD6744412%
      Custer, SD1,7704412%
      Rapid City, SD72,4414412%
      Keystone, SD3184412%

      Cities with similar population

      City, StatePopulationAir Quality IndexNational Avg.
      Cumberland City, TN3184020%
      Diamondhead Lake, IA3183922%
      Eckley, CO3184510%
      Pentress, WV3183628%
      Ballico, CA318484%
      Keystone, SD3184412%
      Source: The Keystone, SD 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.