People seeking drive-up coronavirus tests in Phoenix faced a three-mile-long car line last weekend. On Friday, Arizona’s largest laboratory received twice as many samples as it could process. The phone line for testing appointments at a large site on the state fairgrounds now opens at 7 a.m. with 800 callers already in the queue.

By 7:07 a.m., all 1,000 appointments for the day are typically taken.

“We are literally overwhelmed with the numbers requested,” said Dr. Marjorie Bessel, chief clinical officer at Banner Health, the hospital system that runs the fairground site. “The testing is very popular, and very needed, but we don’t have enough of it.”…

Testing has also become more challenging as temperatures rise. Many health providers run outdoor drive-up sites to lower the risk of disease transmission. That becomes less feasible in the heat, and some testing sites have had to close.