Excessive Heat

Key Points

  • Excessive heat can be a hidden killer. In August 2003, excessive heat killed more than 15,000 people in France. In Cook County, Illinois in 1995, more than 700 deaths were attributed to heat. Because heat does no physical damage and deaths tend to occur in private dwellings, the extent of a heat disaster is often not visible to the public.

  • Since the mid-1970s, an average of three or four heat-related fatalities has occurred each summer in Seattle. During excessively warm summers, such as the summer of 1992, up to 50 to 60 deaths have occurred.

  • The season, humidity, duration and availability of cooling systems all strongly influence the impact of excessive heat events.

  • Seattle's typically mild summers result in a population that is less acclimatized to extreme heat compared with that of many other cities in the United States. Health effects associated with heat begin in Seattle at lower temperatures than many other places. The relative temperature, compared to normal seasonal temperatures, is often more important than the actual temperature. Seattle is among the cities with the highest heat sensitivity in the country.

  • Many Seattle homes and businesses lack cooling systems, increasing our vulnerability.

  • The most vulnerable people in heat events are the elderly, infants, the homeless, the poor and people who are socially isolated.

  • Heat cramps, heat exhaustion, and heat stroke are examples of negative health effects associated with both average warmer summer temperatures and temperature extremes.

  • In Seattle, most fatalities are indirectly caused by heat, e.g., heart attacks, strokes, and respiratory illness.

  • Climate research shows that extreme heat events have become more severe in the Pacific Northwest in recent decades. Experts project that temperatures on the hottest days in the Puget Sound area will increase by 6.5°F on average by 2050.495 Nighttime low temperatures are also increasing, limiting nighttime heat relief.

  • Heat can be costly. The costs of one extreme heat wave in California in 2006 were estimated at over $200 million.

For more information on Excessive Heat Events click here.