The Weather Notebook: Extreme Temps

Extreme Temps
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While wild weather events like tornadoes and floods grab headlines, it's actually the extremes of heat and cold that quietly kill more Americans every year than the higher profile weather events. Hi, I'm Bryan Yeaton for the Weather Notebook. In 1999, for example, weather officials reported 497 heat-related deaths-- five times the year's 92 fatalities from tornadoes.

For the past quarter century, Professor Laurence Kalkstein has led research at the University of Delaware Center for Climatic Research to study the affect of climate on people. He has shown that heat-induced deaths in the US are a grave problem and may increase if projected climate warming becomes reality.

The hazard of hot spells is greater in northeastern cities than in southern ones because southern residents are better acclimatized to long term heat. 92 degrees fahrenheit is the threshold above which mortality spikes dramatically in New York. In contrast, the threshold is 102F in Dallas. And in many northern cities, early-season heat waves are more deadly than identical oppressively hot periods later in the summer because residents haven't yet acclimatized to hot weather stresses.

Kalkstein found a reverse situation for cold-related deaths. Southern cities exhibit the greatest increases in mortality during extreme cold weather, while northern cities showed minimal increases. Again, acclimatization is the key. The threshold temperature for winter mortality in mid-climate cities such as Atlanta is 32F but for northern cities, such as Philadelphia, it is 23F.

Thanks today to writer and meteorologist Keith Heidorn of Victoria, British, Columbia. The Weather Notebook is a production of the Mount Washington Observatory and is supported by Subaru of America. Want more on extremes? Go to our website at mountwashington.org. Thanks today to executive engineer Sean Doucette.