Western heat wave intensifies, desert temperatures could hit 117 degrees

In Phoenix, highs were forecast to reach 110 to 117 degrees Thursday, with morning lows in the 80s to 90s and little overnight recovery for people who spent the day outside or in homes without reliable cooling. Parts of Arizona and California stayed in the triple digits well into the afternoon.

A highly amplified mid-level high-pressure pattern was building across the western and central contiguous U.S. and should persist into mid-July, a setup that tends to lock hot air in place. Maricopa County opened heat relief sites, cooling centers, respite centers and hydration stations for people without access to indoor cool environments, while Phoenix kept a 24-hour respite center at 20 W. Jackson St. and extended hours at Justa Center at 1001 W. Jefferson St. San Diego designated recreation centers, libraries and other public buildings as places to cool down during extreme heat.

Heat risk climbs when unusual heat lasts longer and overnight lows remain high. The National Weather Service urges people to drink fluids, stay in air-conditioned spaces and schedule frequent rest breaks in shaded or cooled areas when working outdoors.

The western surge followed an early-July heat wave that broke nearly 500 daily high-temperature records in the U.S. between July 1 and July 4, left more than 160 million Americans under extreme heat advisories over the July Fourth weekend and caused 32 heat-related deaths in New York and New Jersey. That earlier heat also pushed PJM, the largest U.S. grid operator, toward record demand and emergency curbs, while the broader pattern kept fire danger elevated in the Great Basin and interior Northwest.