More accustomed to the bright lights of the New York night session, the Serbian star instead absorbed the muggy midday August heat, firing off 35 winners to set up a meeting with compatriot Laslo Djere (28) in the third round.
"It has been a tough match especially in the first set with the conditions," said Djokovic, who added that he was able to find his rhythm once the searing sun gave way to a late afternoon shadow across the court.
"I didn't start off the match very well but the second and third set have been at least a couple of levels higher."
A handful of unforced errors were all that separated Djokovic and his unseeded opponent in the first set, as the three-time champion overcame early inaccuracy on his first serve and converted a break point chance in the fourth game.
The Spaniard lost his resolve in the second set, where Djokovic broke in the third and fifth games.
Zapata Miralles helped him break again in the seventh game with a double fault and a clumsy error.
Djokovic saved four break points early in the final set, in which he won the final five games and closed out the match with a forehand winner.
But if he were rattled he scarcely showed it, winning the final five games before closing out the match with a forehand winner.
"One break was enough. Then after that, you know, second set I played really good. Beginning of the third, couple of close games, but last four games of the third I ended up playing really well," he told reporters.
"I'm pleased, you know, I'm pleased with the way I'm feeling, playing on the court."
The Serb is already assured of retaking the world number one spot when the rankings are updated following the tournament after winning his opening match.
He beat his next opponent, the 32nd seed Djere, in their only prior meeting at Belgrade last year.
"It's great for Serbian tennis that we have a matchup in the third round," said Djokovic.
"He's definitely one of the top hardest workers out there. Puts a lot of hours into care for his body and trying to build his form.
"Eventually the results will come for a player like him because he's very, very dedicated."
