Couples, the winner last year at Westchester Country Club in Harrison, N.Y., reached 11-under at Fox Chapel on a day when the temperature reached 96 degrees with a heat index of 105.
Couples is thriving in the heat, in part because it’s better for his chronically bad back.
The 1992 Masters Tournament champion has one bogey.
Joe Daley is a stroke back after 64.
Tom Lehman is in third place, four shots back, after 66.
Augusta native Larry Mize had 65 and is six shots back.
EUROPEAN TOUR: In Portrush, Northern Ireland, Frenchman Gregory Bourdy opened a one-shot lead in the second round of the Irish Open.
Bourdy is at 12-under 132 after 67. Englishman Mark Foster also shot 67 and is in second.
Former Augusta State golfers Jamie Elson (72-79–149) and Scott Jamieson (77-77–154) missed the cut, which fell at 142.
WEB.COM TOUR: In Newburgh, Ind., Australia’s Alistair Presnell shot his second consecutive 4-under-par 68 to take the 36-hole lead in the United Leasing Championship.
Presnell is at 8-under 136 in the inaugural event on the Web.com Tour, formerly the Nationwide Tour.
Former U.S. Open champion Lee Janzen (70 on Friday) and David Lingmerth (70) are one shot back.
Augusta’s Scott Parel birdied his final hole for his second consecutive 71 to make the cut by a shot
North Augusta’s Scott Brown (83-67–150) and Aiken native Matt Hendrix (80-72–152) missed the cut.
LPGA TOUR: In Rogers, Ark., Venezuela’s Veronica Felibert shot 6-under-par 65 to take the first-round lead in the NW Arkansas Classic.
Shanshan Feng, Karine Icher and Mi Jung Hur shot 66s.
Defending champion Yani Tseng had 73.