What you should know about heat deaths as the Western US faces a dangerously hot summer

PHOENIX – A dangerously hot summer is looming across the western United States. Dozens of recent deaths have been blamed on the heat, including retirees in Oregon, a motorcyclist in California’s Death Valley and a 10-year-old boy who collapsed on a Phoenix trail while hiking with his family.

Heat is the leading cause of weather-related deaths nationwide, but because investigations into suspected heat deaths can take months and counties use different methods to count deaths, it is unknown exactly how many people have died in the recent heat wave since July 1.

There is evidence that these were two particularly deadly weeks.

“This is just a harbinger of what is to come,” said Joellen Russell, a climate scientist at the University of Arizona in Tucson, on Friday. “Floods, droughts, wildfires, heat waves, hurricanes, thunderstorms: all of these weather extremes have been caused by the extra carbon dioxide we are releasing into the atmosphere.”

Here are some things you should know:

Where most deaths occurred

In Santa Clara County in Northern California, 19 deaths are being investigated for possible heat-related causes. This month, temperatures soared below 60 degrees following a heat wave. The coroner’s office reported that four of the dead were homeless and nine were over the age of 65.

At least 16 people are said to have died in Oregon due to record high temperatures, most of them in the Portland area.

In Clark County, Nevada, which includes Las Vegas, there have been nine confirmed heat-related deaths this year, the county coroner’s office said.

Several recent deaths involving young children are under investigation in Arizona, including a 2-year-old girl left alone in a hot car outside Tucson and a 4-month-old baby who died after becoming ill on a boat on Lake Havasu.

How hot it was

Record temperatures were broken in the western states this month. Palm Springs in California reached its All-time high of 124 Fahrenheit (51.1 degrees Celsius) on July 5, and Las Vegas recorded its all-time high of 120 F (48.8 degrees Celsius) on July 7.

Las Vegas experienced seven consecutive days of temperatures of 115 degrees Fahrenheit (46.1 degrees Celsius) or higher during the recent heat wave, nearly twice as hot as the old record of four consecutive days set in July 2005, the National Weather Service said. Since June 1, the city has experienced at least 18 heat records.

According to the National Weather Service, a high temperature of 53.8 °C (129 °F) was recorded in Death Valley, California, on July 7, tying the daily record set in 2007. In Phoenix, high temperatures of 46.1 °C (115 °F) were recorded on Wednesday, tying the daily record set in 1958 and 1934.

Portland, Oregon, set new daily high temperature records for five days in a row until Tuesday, when temperatures reached 40 °C (104 °F).

Why the death toll is uncertain

The number of victims of the scorching heat is unknown because each jurisdiction uses different calculation methods, but some counties in the southwestern United States are faring better than most other parts of the country.

Pima County, Arizona’s second-most populous county and home to Tucson, began adding heat-related deaths to a new online dashboard last year. Maricopa County, home to Phoenix, America’s hottest big city, has been tracking heat-related deaths for years. Clark County, Nevada, home to Las Vegas, is now also identifying deaths in which heat was a factor.

But the counting of heat-related deaths is inconsistent across most jurisdictions. In some areas, death investigations are conducted by a medical examiner, usually a doctor trained in forensic pathology. In other areas, the coroner might be an elected sheriff, such as in Orange County, California. In some small counties in Texas, a justice of the peace might determine the cause of death.

Even the Centers for Disease Control and Prevention’s numbers often date back several years and do not provide a complete picture because they rely on information from death certificates, which in turn come from local, state, tribal and territorial databases.

An Associated Press analysis of CDC data this year found that more than 2,300 people who died in the U.S. last summer cited the effects of extreme heat on their death certificates, the highest number in 45 years. Doctors, health experts and meteorologists say that’s only a fraction of the true toll.

Why confirmation is delayed

In some cases, pathologists need months to determine whether a death was caused by heat.

Unlike suicide by hanging or murder by gunshot wound to the head, heat-related death is not always easy to determine. It may take weeks or even months of toxicology testing to determine whether heat played a role.

When a body is found in a hot home days after a death, there are many uncertainties for investigators. Although it may have been very hot when the person was discovered, it is impossible to know how hot a home was when the death occurred.

Toxicological tests can also take a long time to determine the use of substances such as alcohol or street drugs.

Because of this delay, the Maricopa County Health Department was unable to release its final number of 645 heat-related deaths for 2023 until spring. The deaths included deaths in which heat was a secondary factor, such as a heart attack triggered by high temperatures.

The forecast

Temperatures have cooled in Portland, Oregon, but should warm up a bit over the weekend, reaching highs of 35 degrees, extending as far south as Salem and Eugene.

The National Weather Service in Phoenix said an extreme heat warning would be issued through Saturday, with highs reaching 43.8 °C (111 °F) before falling below 43.3 °C (110 °F) on Sunday and into next week.

After 10 days under a warning about excessive heatIn Las Vegas, slightly cooler weather was expected through the weekend. Still, high temperatures for the coming week are expected to remain higher than normal, ranging between 110 and 113 degrees Fahrenheit, the National Weather Service said.

And summer is not over yet.

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Associated Press writers Rio Yamat in Las Vegas and Claire Rush in Portland, Oregon, contributed to this report.