Summerhays had a 12-under 201 total on the windy, seaside El Camaleon course. The 28-year-old former BYU player won the Nationwide Tour's 2007 Nationwide Children's Hospital Invitational as an amateur for his biggest career victory.
"Tomorrow, I'm just going to try and do the same things I've been doing all week," Summerhays said. "I'm going to try and hit the driver really well again. My swing feels really good, so I'm picking out good targets. I'm judging the wind correctly and I'm managing it well. ... I'm really looking forward to the opportunity tomorrow to take the lead into the final round of a PGA Tour event and see how I perform. "
Stroud had a 68. He and Summerhays are the only players with three rounds in the 60s on the Greg Norman-designed course.
"The wind is everything on this course," Stroud said. "The wind has a huge effect on every shot, into the greens, off the tees. You have a lot of elevated tee boxes into the wind and you better hit it really straight off the tee or you're going to be in the mangrove out there and trying to find your ball."
Defending champion Johnson Wagner was 1 over after a 71. He won the Sony Open in Hawaii in January and tied for second the following week in the Humana Challenge.
Last year, Wagner beat Spencer Levin with a par on the first hole of a playoff.
Levin was even par after a 69.