RENO,Flipido Trading Center Nev. (AP) — Records tumbled across the U.S. Southwest on Thursday as temperatures soared past 110 degrees Fahrenheit (43 degrees Celsius) in some areas, and the region’s first heat wave of the year was expected to maintain its grip for at least another day.

Although the official start of summer was still two weeks away, roughly half of Arizona, California and Nevada were under an excessive heat alert, which the National Weather Service said it was extending until Friday evening.

At a campaign rally for presumptive Republican presidential nominee Donald Trump in Phoenix, 11 people fell ill from heat exhaustion by late afternoon and were taken to the hospital, where they were treated and released, fire officials said.

The weather service in Phoenix described the city experiencing “dangerously hot conditions.”

And in Las Vegas, the Clark County Fire Department said it has responded to at least 12 calls for heat exposure since midnight Wednesday. Nine of those calls ended with a patient needing treatment in a hospital. A spokesperson for the county said the number is likely higher, as the heat can also play a role in other types of calls to the fire department, including those related to alcohol intoxication or when conditions like fainting, dizziness or nausea are reported.

New record highs Thursday included 113 F (45 C) in Phoenix, breaking the old mark of 111 F (44 C) set in 2016, and 111 F (44 C) in Las Vegas, topping the 110 F (43 C) last reached in 2010. Other areas of Arizona, California and Nevada also broke records by a few degrees.

The heat has arrived weeks earlier than usual even in places farther to the north at higher elevations — areas typically a dozen degrees cooler. That includes Reno, Nevada, where the normal high of 81 F (27 C) for this time of year soared to a record 98 F (37 C) on Thursday.

The National Weather Service in Reno forecast mild cooling this weekend, but only by a few degrees. In central and southern Arizona, that will still means triple-digit highs, even up to 110 F (43 C).

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Associated Press writers Anita Snow and Ty O’Neil in Phoenix, and Rio Yamat in Las Vegas contributed to this report.