Health risks linked to extreme heat linger even as temperatures drop


A dangerous heat wave imperiling people on the West Coast is expected to peak Saturday, but experts say the health risks will persist long after temperatures crest.

“Widespread temperature records are expected to be tied or broken. Saturday will likely shape up to be the hottest day in this heatwave when high temperatures into the 110s will be common across California,” forecasters said in their nationwide update Friday. “The duration of this heat is also concerning as scorching above average temperatures are forecast to linger into next week.” 

Heat accumulates over time in people’s bodies, and the risk of a heart attack, heatstroke or other medical ailment often rises over time. Some experts said medical risks due to heat often trail behind the rise in temperatures — but spike as the days of risk add up.

“Usually you see deaths from heat waves not from the first day, but on the second and third day,” said Dr. Lisa Patel, a clinical associate professor who practices as a pediatrician at Stanford Medicine Children’s Health. “The cumulative heat is a big risk factor, especially for the elderly and for chronic health conditions.”

A farmworker operates a tractor
A farm at sunrise near Coachella, Calif., on July 3.Mario Tama / Getty Images

In this case, the extreme heat is forecast to persist for more than a week without a break, grinding away at people’s resilience. The National Weather Service forecast on Friday called for record-breaking temperatures in California, Oregon and Washington on Saturday.

In areas like the Sacramento Valley, where the heat wave has been centered, the National Weather Service put advisories in place on Tuesday morning at 11 a.m. Those advisories will last through next Tuesday, at least.

“Early next week into next week there are hints of relief,” said Dakari Anderson, a meteorologist with the National Weather Service in California’s capital city, adding that “relief will be a relative term” and temperatures could still be above 100 degrees in parts of the region.

In the U.S., heat is the leading weather-related cause of death. Its effects are sometimes underestimated in statistics because it often worsens underlying ailments like heart disease, respiratory problems or kidney disease.

Aconstruction worker drinks water
A construction worker in Folsom, Calif., on July 3.David Paul Morris / Bloomberg via Getty Images

Daily emergency department admissions for heat-related illness have soared in recent days, according to data from the Centers for Disease Control and Prevention. 

On July 4, heat-related illness accounted for nearly 1.1% of all emergency department visits in a region that includes California, Arizona and Nevada. The rate of visits for heat-related illness had more than doubled since July 1, the data shows.

A map of heat risk, published jointly by the National Weather Service and the CDC, shows that some parts of California, including parts of the San Joaquin valley, should expect to face “extreme” conditions every day next week. The designation means the agencies expect impacts on health care facilities and infrastructure.

In Portland, Oregon, where temperatures are expected to rise above 100 degrees Saturday, Dr. Richard Bruno, the Multnomah County health officer, said he was concerned because Portlanders had experienced so few hot days this year and their bodies had not yet acclimated to heat.

“I’m particularly worried about the thousands of people heading to music festivals and sporting events this weekend,” Bruno said in a news release. “They’ll be spending a long time outside, may have little access to shade and water, and may not recognize the risk.”

Death Valley could reach 130 degrees on Sunday. Such temperatures exceed the limits where some people can survive, even if they don’t have a specific, chronic health condition, according to Jennifer Vanos, an associate professor in the School of Sustainability at Arizona State University.

Vanos, who studies the limits of human physiology in heat, built a model of survival thresholds that factors in humidity, temperature, age and time. She said exposure to the kinds of conditions forecast for Death Valley on Sunday would likely cause death by heatstroke within six hours for an elderly person, even if they’re inside a building or in the shade, assuming they can’t access air conditioning.

Even in dry desert conditions, Vanos said, older people’s bodies simply can’t keep up with cooling demands in those temperatures.

“We can only sweat so much, and older people even less,” Vanos said in an email.



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