The Latest: Extreme heat policy in effect again at US Open

              A fan shelters under an umbrella and sips a drink as she watches the match between Fabio Fognini, of Italy, and Michael Mmoh during the first round of the U.S. Open tennis tournament, Tuesday, Aug. 28, 2018, in New York. (AP Photo/Julio Cortez)

NEW YORK (AP) — The Latest on the U.S. Open tennis tournament (all times local):

1:10 a.m.

Two-time major champion Garbine Muguruza let a lead slip away and was stunned in the second round of the U.S. Open by 202nd-ranked Czech qualifier Karolina Muchova 3-6, 6-4, 6-4.

The 12th-seeded Muguruza was up a set and a break in the second but faltered.

Muchova is playing in the main draw of a Grand Slam tournament for the first time.

Muguruza, in contrast, won titles at the French Open in 2016 and Wimbledon in 2017 and has been ranked No. 1.

“Somehow, I made it. I don’t know how,” Muchova told the Louis Armstrong Stadium crowd.

The match lasted nearly 2½ hours and ended a little past 1 a.m. on Thursday.