In the middle of September, with the temperature in the upper 80s and the heat of battle over 100, Angelique Kerber did a snow angel.

Laying on her back on the baseline of Arthur Ashe Stadium, limbs akimbo, Kerber was in the first throes of emotion after winning the U.S. Open Saturday. Karolina Pliskova’s shot sailed long and Kerber’s career, already at an all-time high, sailed to its apex. That’s when she dropped to her back in celebration.

With a 6-3, 4-6, 6-4 victory over the surprising Pliskova, Kerber bookended the Gram Slam season with her second major of the year after winning her first ever Slam at the Australian Open in January. She also made the final of Wimbledon where she was beaten by Serena Williams. When Williams was beaten by Pliskova in a semifinal here, it assured that Kerber would displace Williams as the No. 1 player in the world, a ranking she has held for 186 weeks.

“It’s just incredible what I did this year,” Kerber said. “I’m really so happy and so proud about everything what’s happened now about my team, about my game, and about my improvement. I think I improved a lot in a lot of ways. To being here with my second trophy, it’s just the best feeling ever.”

What a run it was for Pliskova, the 10th seed and 11th-ranked player in the world. She was the only player ranked in the top 20 who had never before reached the fourth round of a Slam.

Then at the Open all the elements of her power game came together. She defeated Venus Williams in her first ever fourth-round appearance, fighting off a match point. In her first quarterfinal she beat rising teenager Ana Konjuh. In her first semifinal, she handled Serena Williams. And Saturday, she was very much the equal of the superb Kerber.

advertisement | advertise on newsday

One glaring statistic that defined the match, which Kerber at no point was dominating, was unforced errors: Pliskova made 47, Kerber 17. Kerber dealt with Pliskova’s big serve, returning her first serve well and making hay off her second serve. Kerber, who is a powder puff server by comparison, won 53 percent of her second serve points while Pliskova won only 39 percent of hers. Kerber won four of five break points against Pliskova while Pliskova won only two of seven.

Because Kerber is lefthanded (the fourth lefthanded woman to win the Open), her serve was unusually effective.

“I didn’t play a lefty girl in this tournament so far, I think, so it’s always different to play lefty, you know,” Pliskova said. “She’s always serving to the backhand. You cannot do much from it. Then she has the whole court open.”

She beat Kerber in the Cincinnati final, the biggest win of her career, and now has followed it up with her finest performance in a Grand Slam. She takes away a boatload of confidence. “You don’t have much matches like this in your career or in the whole year. So I definitely take on a positive,” said the 24-year-old Czech. “The next Grand Slam I’m trying — I’m going to try to play like I was playing here from the first round to the last one.”

At 28, Kerber becomes the second German No. 1 player after the legendary Steffi Graf. She has steadily ramped up her game to be more than just a defender. Her coach, Torben Beltz, said that offseason hitting sessions with two partners late in the year put Kerber in a more offensive mind. “These days you have to play aggressive. These days you can’t win by just putting the ball in,” he said. “I think it’s very important to change up, to be offensive, defensive then offensive again and she has learned pretty good, that’s why she is so successful.”

@NewsdaySports

Body language has been an issue for Kerber, something she has fought to overcome. It was turning foul in the second set Saturday, but at the end her snow angel spoke volumes.