Kenya's Olympic champion David Rudisha also outclassed his opponents to easily win the 800m at the New York leg of the Diamond League series.
Croatia's Blanka Vlasic, competing for the first time since 2011, won the women's high jump while veteran Jamaican sprinter Veronica Campbell-Brown showed a clean pair of heels to win the women's 200m dash.
Despite running into a headwind on a cold and rainy day in Manhattan, Gay won the men's sprint in 10.02 seconds, well outside his world leading season-best of 9.86 but still enough for a comfortable win.
"I'm happy with that," said the 31-year-old American, who has been plagued by injuries since winning the world title in 2007. "I didn't try to push myself too hard in these conditions."
Rudisha, who produced one of the greatest performances in middle-distance running when he broke his own world record to win gold at last year's London Olympics, also ran within himself to win the two-lap race at Randall's Island.
The 24-year-old, who has struggled before in the rain, stopped the clock at 1:45.14 to capture his second Diamond League title this month after winning in Doha two weeks ago.
"The time does not matter," he said. "It was cold and there was a strong wind down the back straight. It was very tough.
"The main target for me this year is the world championships."
Vlasic made a triumphant return to competition after a leg injury kept her sidelined for nearly two years, ruining her hopes of competing at the London Olympics.
The four-time world champion was a bundle of nerves as she lined up on the runway for her first jump but produced a flawless performance, clearing each of the six heights she attempted, including a best of 1.94m.
"I can't even begin to explain how scared I was," she told reporters. "I really didn't know if I was ready or not because in training I've still been in a lot of pain.
"So this is just a dream for me to win under these circumstances."
Campbell-Brown, a two-time Olympic champion, won the women's 200 in 22.53 seconds, her best this season, while American Olympic champion Jennifer Suhr won the women's pole vault, which the gusting winds played havoc, with a best clearance of 4.63m.
American Olympic long jump champion Brittney Reese struggled in the conditions, failing to make it past the first round of jumps, while 400m Olympic gold medallist Sanya Richards-Ross, who was due to make her first appearance since London after undergoing toe surgery, pulled out before her race.
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