TULSA, Okla. — One last birdie in a strong Oklahoma wind gave Justin Thomas another 3-under 67 and set a daunting target for Rory McIlroy and everyone else Friday in the PGA Championship.

Trees were swaying and flags were whipping from the opening tee shot, and rounds in the 60s were scarce at Southern Hills.

That didn’t stop Thomas, who leaned on creativity with the shape of his shots, even on the putting green. He dropped only one shot, from a bunker on the par-3 14th, and finished his solid round with a 10-foot birdie putt.

That put him at 6-under 134, 1 shot ahead of McIlroy, who was making his way to the first tee shortly after Thomas finished.

McIlroy and Tiger Woods faced what typically are tougher conditions in the afternoon, though the forecast was for the wind to die. Jon Rahm, who fought back with a 69, wasn’t buying it.

“They said the wind was going to go down this afternoon. No, it’s not. It’s Oklahoma,” Rahm said. “It’s going to stay just as windy as we had.”

Thomas can only hope that’s the case. The heritage of Southern Hills is that all seven of its major champions — three in the U.S. Open, four in the PGA — have had at least a share of the 36-hole lead.

“If I maintain the lead, I hope that trend continues,” Thomas said.

Of those who played Friday morning, Thomas had a 3-shot lead over Matt Fitzpatrick (69), who has never won in America but seems to play his best the tougher the conditions.

The only other players from that early group who finished two rounds under par were Oklahoma-born Talor Gooch, who had 16 pars, one birdie and one bogey in a round of 70; Joaquin Niemann of Chile (71); and Bernd Wiesberger of Austria (67). They were at 1-under 139.

McIlroy was in the same group as Woods and Jordan Spieth, one of them trying to stay near the top, the other two hopeful of making it to the weekend. Woods opened with a 74, which was looking to be around the cut line.

Thomas was not trending all that well coming into the only major he has won, the 2017 PGA Championship at Quail Hollow. He has gone 14 months without winning. He was not feeling his best earlier in the week, a combination of a viral infection and allergies.

All that has changed on a course he saw for the first time last week when he joined Spieth for a practice round. He opened with a pair of short birdies on No. 10 and the par-5 13th, with a tough par along the way that illustrated the effect of the wind. From 50 feet away on the 12th green, he sent the putt well out to the right and let the wind push it back toward the hole. He still had 6 feet and made that for par.

Thomas holed a 25-foot birdie on the par-5 fifth and closed out his round with his fourth birdie. He gave respect to every shot, even putts that ordinarily would have been treated like tap-ins.

“Although I played solid yesterday, I played really, really well today,” Thomas said. “The conditions were obviously very difficult. I stayed very patient, tried to get in my own little world and get in a zone and just tried to execute each shot the best I could.

“I’m glad to have a good round to show for it.”

The strength of the wind could have a big impact on who sticks around for the weekend. Masters champion Scottie Scheffler three-putted for double bogey on No. 9 to cap a 75 that left him at 6-over 146 and very much in danger of missing the cut.

Dustin Johnson had another 73 and was in the same predicament. At least they had hope. Patrick Cantlay had a 75 and was 11 over, the first time he will miss the cut in the PGA.

Brooks Koepka avoided such a fate with a 67, matching Thomas and Wiesberger for the low score of the morning. The difference from an opening 75 was easy for him to decipher.

“You can’t play from the rough. Simple,” Koepka said. “If you’re going to put it in the rough, it’s going to be quite difficult to even get the ball close.”