Pegula, Muchova in a hurry at Flushing Meadows

Seeded players Jessica Pegula and Karolina Muchova have dispatched of their opposition in lightning-quick time to reach the third round of the US Open.

No.3 seed Pegula needed only 56 minutes on Wednesday to defeat Sofia Kenin 6-3 6-1, after the 2020 Australian Open champion beat Venus Williams in her first match.

"To be out of there in under an hour, it doesn't always happen," Pegula said. "So I think I'm just going to take that one and run, I guess, until the next round."

World No.7 Karolina Muchova stormed into the third round with a crushing 6-1 6-0 victory over Britain's Katie Boulter.

Rain forced the meeting to be moved to the roofed Louis Armstrong Stadium and the two-time semi-finalist at Flushing Meadows was ruthless from start to finish.

World No.62 Boulter, who recently married Australian tennis ace Alex de Minaur, briefly threatened to make a contest of it by breaking Muchova's first service game, but she struggled to find any rhythm after that.

Muchova recovered immediately and took full advantage of Boulter's unforced errors, 15 of which came in the first set alone, to take the opener.

The second followed much the same script, with the Czech continuing to dictate play while Boulter failed to hold serve throughout the match, allowing Muchova to secure the win in under an hour.

"I was happy about my composure. We changed courts to this one with the roof, so of course I'm really happy with the way I adapted," Muchova said on court.

Muchova, who claimed the mixed doubles title in New York with compatriot Jakub Mensik, will next face the winner of the all-American clash between Emma Navarro and Caty McNally.

With rain coming down for a second day in New York, play was suspended again for a time on outside courts, allowing only play under the roofs in Arthur Ashe Stadium and Louis Armstrong Stadium to continue uninterrupted.

Those are second-round matches, while some players were still playing their first. When the US Open switched to a Sunday start last year, it spread out the first round over the first three days, so Wednesday would have arrived with everyone playing in the second round had the weather cooperated.

It hadn't, and some players were not only still playing their first match, but they had to hope the weather cleared enough later so they wouldn't have to resume it Thursday.

That poses a mental challenge, with Paula Badosa saying she didn't even know how to prepare for the resumption of her match against Australian Daria Kasatkina, which was halted Tuesday with her one game from winning to set up a second-round match against No.4 Coco Gauff.