Where Are the Highest Chances for a Hot Summer in 2017?

Schools are letting out, Memorial Day is here, and for many Americans that means the unofficial start of summer.

And if it’s summer, then it ‘s time to start paying attention to the risk of extreme heat.

According to NOAA’s summer outlook, most of the United States is favored to have a hotter than average summer in 2017. Only in the Great Plains do forecasters think the chances for a cool or a normal summer are equal to the chances of a hot summer. Everywhere else—from Alaska to southern California, and from Maine to Texas—odds are tilted toward well above average warmth. The absolute highest chances for a much warmer than usual summer are in Hawaii.

Map showing the odds of well above average temperature during summer of 2017. Well above average means “in the upper third of the 1981-2010 climate record.” White shows areas with equal chances for any of the possible climate outcomes (cool, warm, or normal). Darker red colors mean higher chances (greater confidence). NOAA Climate.gov map, based on data from the Climate Prediction Center.

The orange and red colors on the map show where the chances of a much warmer than average summer exceed 33%. The darker the color, the greater the chances. Areas colored white mean that forecasters think all three temperatures possibilities—colder than normal, near normal, and hotter than normal—have an equal chance of occurring. In other words, the climate system is not leaning one way or another.

A static map can only show the percent chance for one of the three possible temperature outcomes, so the colors are determined by which outcome is more likely. That doesn’t mean there is no chance of a normal or even a cooler than normal summer.  The complete forecast includes the odds of all three temperature (and precipitation) categories.  (We covered this in more detail in last year’s summer outlook if you want to dig into the math). NOAA’s Climate Prediction Center, which issues these forecasts, is experimenting with interactive maps as a way of sharing the full suite of forecast probabilities.

When it comes to heat stress, nighttime matters, too

There is more than one way to define a “heat wave,” since what counts as “extreme heat” depends not just on location and air temperatures, but also on how humid it is, whether there is a breeze, and how sunny or overcast it is. One factor that public health experts say is critical is the overnight low temperature. When it doesn’t cool off at night for at least a few hours, an extended hot spell can become especially dangerous. It’s a situation that global warming is making more common.

If you are interested in learning more about tools and strategies for protecting yourself or your community from heat-related illnesses this summer, hop on over to the U.S. Climate Resilience Toolkit and check out the resources available from the National Integrated Heat Health Information System (NIHHIS), a collaboration between NOAA, the CDC, FEMA, and other partners.  A portal to all things heat health, NIHHIS was created to help decisions makers prepare for extreme heat events days, months, and years into the future.

Visit www.climate.gov for additional information.