Rick Price and Bob Heintz each shot 5-under 67 and share second place at 8-under-par 136. Craig Kanada is one stroke further back after a 3-under 69.
Charlie Wi fired a 6-under 66 and stands alongside Rich Barcelo, Danny Briggs, Tom Scherrer and John Mallinger in fourth place at minus-6.
Weekley started on the back nine Friday and got going with a 3-foot birdie putt on the 11th. He sank back-to-back birdies from the 13th, from six and five feet respectively, to move to 8 under.
The 33-year-old parred five in a row around the turn. Weekley tripped to a bogey on the second, but atoned for that mistake at the fifth. He got up and down for birdie on five, then birdied No. 6 to climb to minus-9.
Weekley pitched his third to 3 feet at the par-5 eighth and kicked that in for his final birdie.
'I struck the ball well today. The putts weren't falling. Then I caught a break on No. 4 when my ball hit a hazard line and bounced through the green,' said Weekley. 'I've had the lead or been tied for the lead twice, I just have to keep it in front of me.'
Price was even-par after nine holes with three birdies and three bogeys on his front nine. He birdied the 11th, then ran off three straight birdies from the 13th. Price closed with a birdie on 18 to share second.
Heintz birdied three of the first five holes, then got to 7 under with a birdie on eight. He faltered to a bogey on nine, but birdied 11 and 13. Heintz tripped to another bogey at 14, but birdied the 15th to earn a share of second place.
There are 15 players tied for 10th place at 5-under-par 139. Among them is Johnson Wagner, the tour's leading money winner.
Ken Duke carded a rare double-eagle, or albatross, on the par-five eighth. He holed a 4-iron from 216 yards out for the first double-eagle of his career and shares 25th place at minus-four with first-round leader Michael Long and nine other players.
'I eagled that hole on Thursday so five shots (under-par) so far this week on a par-5 is pretty good,' Duke joked. 'It hit six or seven feet short, took the slope and rolled in the hole. I've had seven aces in my career, never a double-eagle before.'
The cut line fell at 2-under-par 142 with 60 players moving on to the final two rounds.