The heat is on: global warming could mean many more days over 90, 95, and 100°F for the USA

Unless climate change is controlled severe heat waves and health threats could become common.

provided by Environmental Defense Fund
  n analysis released today by the Environmental Defense Fund (EDF) shows that US cities are expected to experience many more days over 90, 95 and 100°F in the future than they currently average unless swift action is taken to bring global warming under control. The analysis is available free at on the World Wide Web.

"This year's devastating heat waves and tragic heat-related deaths may provide a picture of a typical summer of the future unless emissions of greenhouse gases are significantly reduced," said EDF scientist Dr. Janine Bloomfield. "Our analysis shows that without greenhouse gas controls many cities across the US can be expected to experience a substantial increase in very warm days by the year 2100. Children, the elderly and those already weakened by illness are especially vulnerable to heat-related illness and even mortality during prolonged periods of hot weather."

For example, the medium warming scenario (plus 3.6°F) shows the following yearly averages:

  • Miami currently averages 23 days over 90°F, by 2100 it could average 121, a 98 day increase
  • Houston currently averages 89 days over 90°F, by 2100 it could average 132, a 43 day increase
  • Washington, DC currently averages 32 days over 90°F, by 2100 it could average 58, a 26 day increase
  The analysis is based on the range of findings of the UN Intergovernmental Panel on Climate Change (IPCC), an international group of thousands of scientists advising governments on the scientific consensus on climate change, and historical weather data from the National Center for Atmospheric Research. The weather data were used to establish the annual average number of days selected cities experienced temperatures exceeding 90, 95, and 100°F. These averages were compared to three scenarios for climate change that span the IPCC range of scenarios for the year 2100: increases over current average temperatures of 1.8°F. (low), 3.6°F. (medium), and 5.4°F. (high). The medium scenario represents the IPCC's current best estimate of projected temperature increases for the year 2100 due to global climate change.

The analysis also ranks 34 cities by their increase in number of days over 90, 95, and 100°F. using the medium warming scenario (plus 3.6°F). The rankings are available free at on the Web.

"If we want our grandchildren to inherit a safe and stable climate, it's critical that affordable early reductions of greenhouse gas emissions be started immediately," said Bloomfield.


Projected Days Per Year Over 90°F By The Year 2100

Selected U.S. Cities Ranked By Increase in Total Number Of Days
Using The Mediam Warming Scenario (Plus 3.6°F)

Rank City Current Average Additional Days Over 90°F Rank City Current Average Additional Days Over 90°F
1 Miami 23 98 16 Des Moines 20 22
2 Daytona Beach 36 74 16 Phoenix 161 22
3 Charleston 5 46 17 Dayton 12 20
4 Houston 89 43 18 New York 13 19
5 San Antonio 101 39 19 Chicago 15 18
6 Albuquerque 58 33 20 Pittsburg 8 15
7 Richmond 36 32 20 Fargo 11 15
8 St. Louis 36 31 21 Cleveland 7 14
9 Louisville 29 30 22 Boston 11 13
10 Dallas 90 28 23 Milwaukee 8 11
11 Kansas City 36 27 23 Portland 11 11
12 Baltimore 26 26 24 Buffalo 2 10
12 Washington, D.C. 32 26 25 San Diego 3 4
13 Indianapolis 14 25 26 Los Angeles 3 3
14 Philadelphia 21 24 27 Seattle 3 3
15 Columbus 14 23
15 Cincinnati 15 23

  The Environmental Defense Fund, a leading national, NY-based nonprofit organization, represents 300,000 members. EDF links science, economics and law to create innovative, equitable and economically viable solutions to today's environmental problems