Weir had eight birdies and a bogey at En-Joie Golf Club in the round delayed by rain for about two hours to reach 12-under 132.
“The nice part of where I was on the weather delay, I had hit my tee shot on the eighth hole, so I was down there with just a rescue club from 218 yards or 220 yards,” Weir said. “It was a nice comfortable shot for me coming out of the rain delay. It was just a comfortable rescue club. I hit a nice shot to 20 feet for eagle and left it just short right in the middle, but it was a nice birdie and nice momentum coming off to keep the birdie momentum going.”
The 52-year-old Canadian left-hander won the rain-shortened Insperity Invitational last year for his lone senior title.
“I’m sure I’m going to have to shoot 6 or 7 under tomorrow with the guys that are up near the top, a lot of firepower there,” Weir said. “There’ll be no coasting, we’re going to be trying to make some birdies and keep some momentum going.”
The 50-year-old Harrington had a 67. The Irishman won the U.S. Senior Open in late June at Saucon Valley for his first victory on the 50-and-over tour.