Triple-digit temperatures to hit parts of California and Arizona in early-season heat wave

By Monday morning, firefighters had developed a containment line around three-quarters of the fire.  

“Humidities are starting to drop,” Kurth said. “We have seen an uptick in grass fires.”

He noted that the heat wave beginning this week wouldn’t be uncommon for August in central California, but he said its early nature could make it more significant because “people aren’t adjusted to the heat.”

“When we get an earlier season heat event, it can have more impact on people,” he said. 

In mountainous areas of the West, he said, early-season waves can also increase drowning risks, because people often flock to rivers running with fresh snowmelt. 

“We have some pretty cold temperatures in the water and strong currents,” Kurth said. “Be careful; wear life vests.” 

The National Oceanic and Atmospheric Administration predicted last month that 2024 will be one of the five warmest years in recorded history and said it has a decent chance to be the hottest on record.

Last year, deaths spiked as prolonged heat waves battered much of the South and the Southwest.

Adrian Mata stands in a sliver of shade while waiting for the bus in Phoenix on July 15.Brandon Bell / Getty Images file

The death certificates of more than 2,300 people who died in the U.S. last summer mentioned heat, according to an Associated Press analysis of Centers for Disease Control and Prevention data — the most in 45 years. 

Heat is the leading weather-related cause of death in the U.S. But its consequences are sometimes obscured in death certificate data because heat often aggravates underlying conditions, such as heart disease, respiratory problems or kidney disease. Texas A&M researchers estimated that 11,000 people most likely died who otherwise wouldn't have because of heat last year, the AP reported. 

Weather patterns like the high-pressure ridge expected to form this week were to blame for many of those deaths. 

The Phoenix area endured temperatures above 110 degrees on all but one day of July last year, according to National Weather Service data — something scientists have since determined was “virtually impossible” but for the effects of climate change. In Maricopa County, home to Phoenix and many of its suburbs, at least 645 people died from heat-related causes last year, a 52% increase over the previous year.