The roof was closed at Arthur Ashe Stadium as Nadal improved to 13-0 in U.S. Open first-round play by dispatching Serbian Dusan Lajovic 7-6 (6), 6-2, 6-2 at New York.
Nadal struggled early in the match and uncharacteristically had more unforced errors (34) than winners (33).
But he recovered from the shaky first set to roll through the following two.
"I need to keep improving," Nadal said in a post-match television interview. "The first round is never easy. There are nerves to play in this amazing place."
Nadal, who had five aces, admitted to struggling with the acoustics after the roof was shut. He said the stadium is vastly different when it doesn't have its open-air feel.
"There is a lot of noise when the roof is closed," the Spaniard said. "Big change."
The only other men's match to avoid postponement on Tuesday is the late affair between third-seeded Swiss star Roger Federer and American Frances Tiafoe. It also will be played at Arthur Ashe Stadium.
With the rain wreaking havoc, Nadal won't learn his second-round opponent until sometime Tuesday, weather permitting.
He will face the winner of the match between American Tommy Paul and Japan's Taro Daniel.
"I try to focus on doing my work well," Nadal said. "I'm happy to have one day off to keep practicing."