Records tumbled across the Southwest United States on Thursday as temperatures soared past 110 degrees Fahrenheit (43 degrees Celsius) from southeast California to Arizona, where 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 is still two weeks away, roughly half of Arizona and Nevada were under an excessive heat alert, which the National Weather Service said it was extending until Friday evening. The heat alert for Las Vegas was extended through Saturday.