Heat Dome in Southwest Keeps Temps At or Near 100 Degrees for Days on End

Map: CBS News

Temperatures are forecast to continue to exceed 110 degrees across the Southwestern U.S. this week — Phoenix might set a record for its all-time high. But it’s not only going to bake the South — the heatwave will cause 100-degree temperatures across the Ohio Valley and into the Mid-Atlantic.  According to CBS News, “the National Weather Service is forecasting 75 or more record-high temperatures to be approached or broken from Friday to Tuesday alone, and that number is likely to grow significantly into next week.”  At the same time, NOAA forecast that a “La Niña” (cooling of the ocean near the equator in the Pacific) could develop later this year increasing the likelihood of fall hurricanes, as well as a colder winter for some parts of the country.   

Why This Matters:  The very areas of the country that are being ravaged by COVID-19 are now experiencing the worst of the heatwave too.  This pattern of super-hot summers, that may be here to stay thanks to climate change, is also quite dangerous and will result in more heat illness.  Over the past few years, these massive heat outbreaks, known as heat domes, create hot and dry conditions for days.  Most of the U.S. will be impacted — 265 million people — will sweat through highs above 90 within the next week, PLUS another 45 million will suffer through triple-digit temperatures.  And it could get worse for other COVID hotspots if hurricane season is active.

Under the Heat Dome

The prolonged exposure to excessive heat is the biggest concern for Jeff Masters, Ph.D., founder of the popular site website Weather Underground and a regular contributor to Yale Climate Connections.  He told CBS that “[t]he heatwave will be very long-lived, lasting multiple weeks in some areas with only a few days of near-normal temperatures during that span. This will increase the odds of heat illness and heat-related deaths.”  With the Weather Service issuing an Excessive Heat Warning for inland Southern California, southern Nevada, and the southern half of Arizona through today people are at great risk of heat-related illnesses such as heat cramps, heat exhaustion, and heatstroke.  The heat has extended north this summer too — the surface temperatures of the water in the Great Lakes is much higher than usual, according to Michigan Live news —  the water in Lake Michigan is 11 degrees warmer than usual and in Lake Huron, it is 8 degrees warmer.  And Washington, D.C. has had 14 consecutive days of 90 degrees plus high temperatures, which is near the record.

Ls Niña On The Way?

There is at least a good chance that we will have a La Niña this year, according to the National Oceanic and Atmospheric Administration (NOAA).  The Weather Channel reported on Friday that NOAA predicts that there is a 50% to 55% chance that La Niña conditions will develop by this fall and persist through the winter ahead.  As a result, experts are now expecting an active hurricane season — again bad news for COVID hot spots like Florida, Georgia, and the Carolinas.  According to The Weather Channel, a “La Niña typically corresponds with a more active hurricane season because the cooler waters of the Eastern Pacific Ocean cause less wind shear and weaker low-level winds in the Caribbean Sea. La Niña can also enhance rising motion over the Atlantic Basin, making it easier for storms to develop.”

Graphic: National Weather Service via Twitter

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