TODAY APR12
TEMPERATURE59
HUMIDITY48
PRESSURE101625.52
WIND COND.
  • 8162Sat
  • 8460Sun
  • 8566Mon40%
  • 8062Tue60%60%
  • 8260Wed30%
daynightWeather update from St. Louis Regional Airport at
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Weather Quick Facts

  • The highest monthly average temperature in Alton for July is 76.5 degrees
  • The lowest monthly average temperature in Alton for January is 31.2 degrees
  • The most monthly precipitation in Alton occurs in July with 7.3 inches
  • The air quality index in Alton is 28% worse than the national average
  • The pollution index in Alton is 211% worse than the national average

Compare Alton, IL Weather

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      Alton 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°F31°F3.4"
      February25°F43°F33°F3.7"
      March38°F57°F46°F3.1"
      April47°F68°F56°F6.6"
      May56°F76°F65°F6.1"
      June65°F85°F75°F3.5"
      July67°F87°F77°F7.3"
      August66°F86°F75°F6.8"
      September58°F80°F68°F4.4"
      October47°F68°F57°F6.7"
      November36°F56°F45°F4.9"
      December28°F43°F35°F6.3"

      Alton 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.
      IndexAltonIllinoisNational
      Air quality index544142
      Pollution index8,473,0503,148,6942,726,193

      Alton air quality information

      MeasurementTotal
      Days measured365
      Days with good air quality134
      Days with moderate air quality221
      Days w/ poor A.Q. for sensitive groups8
      Days with unhealthy air quality2

      Alton air quality information

      PollutantTotal
      Arsenic0.020%
      Benzene0.070%
      Carbon Tetrachloride0.020%
      Lead0.010%
      Mercury0.010%

      Average monthly Alton temperature with heat index

      Alton monthly precipitation with daily maximum

      Alton monthly snow depth with daily maximum

      Alton monthly wind speed information

      Nearby cities with good air quality

      CityPopulationAir Quality IndexNational Avg.
      Hillsdale, MO1,029548.0%
      Velda City, MO1,421548.0%
      Berkeley, MO8,912548.0%
      Dellwood, MO5,010548.0%
      Hazelwood, MO25,222548.0%
      Alton, IL26,490548.0%

      Cities with similar population

      CityPopulationAir Quality IndexNational Avg.
      Conception Bay South, NL26,497n/a 
      Batavia, IL26,4795510.0%
      Pearl, MS26,4624412.0%
      Wooster, OH26,5574314.0%
      Brownsburg, IN26,560548.0%
      Alton, IL26,490548.0%
      Source: The Alton, IL 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.