Extreme Heat – Aspects and Features


hot-heat-extreme-heat-heatwaveHeat is the number one weather-related killer in the U.S., resulting in hundreds of fatalities each year.[1] Conditions involving high air temperatures, radiant heat sources, high humidity, direct physical contact with hot objects, or strenuous physical activities have a high potential for causing heat-related illness.[2]

Other conditions that contribute to heat-related illnesses include stagnant atmospheric conditions and poor air quality. Consequently, people living in urban areas may be at greater risk from the effects of a prolonged heat wave than those living in rural areas. Also, asphalt and concrete store heat longer and gradually release heat at night, which can produce higher nighttime temperatures known as the “urban heat island effect”.[3]

The stagnant atmospheric conditions of the heat wave trap pollutants in urban areas and add the stresses of severe pollution to the already dangerous stresses of hot weather, creating a health problem of undiscovered dimensions. The high inner-city death rates also can be read as poor access to air-conditioned rooms. While air conditioning may be a luxury in normal times, it can be a lifesaver during heat wave conditions.[4]

Heat Index Chart

NOAA’s heat alert procedures are based mainly on Heat Index Values. The Heat Index is an index that combines air temperature and relative humidity in an attempt to determine the human-perceived equivalent temperature—how hot it feels. The result is also known as the “felt air temperature” or “apparent temperature”. Since heat index values are devised for shady, light wind conditions, exposure to full sunshine can increase heat index values by up to 15°F. Also, strong winds, particularly with very hot, dry air, can be extremely hazardous. To determine heat index, use chart below:[6]

NOAA Heat Index Chart[7]


  1. NOAA Watch – Heat Wave: A Major Summer Killer: http://www.noaawatch.gov/themes/heat.php
  2. Occupational Safety & Health Administration (OSHA) – Occupational Heat Wave: https://www.osha.gov/SLTC/heatstress/
  3. Ready.gov – Extreme Heat: http://www.ready.gov/heat
  4. NOAA – NWS – Office of Climate, Water, and Weather Services – Heat: A Major Killer: http://www.nws.noaa.gov/os/heat/index.shtml
  5. Image Source: http://www.crh.noaa.gov/images/dmx/Preparedness/Heat2R.jpg [Accessed August 17, 2013]
  6. NOAA – NWS – Office of Climate, Water, and Weather Services – Heat: A Major Killer: http://www.nws.noaa.gov/os/heat/index.shtml
  7. Image Source: http://www.nws.noaa.gov/os/heat/index.shtml [Accessed August 17, 2013]