A weather delay of more than six hours pushed most tee times after 1:30 p.m. (local time) and left a small window of daylight for players to attempt to complete their round.
Only 41 players finished, leaving 37 to return Sunday morning.
Watson was at 15 under with three holes remaining when play was suspended. He made the last of his 10 birdies on a 4-foot putt at No. 15 to take a three shot lead over Jeff Maggert.
Maggert rolled in a 26-foot birdie at No. 14, his seventh birdie Saturday, to reach 12-under. The three-time Houston Open runner-up was also through 15 holes.
Adam Scott (65), Paul Stankowski (65) and Johnson Wagner (64) held the clubhouse lead at 11-under 205.
Scott and Stankowski played together and had nearly identical scorecards, posting seven birdies without a bogey for their 65s.
'You have to trust yourself when you can't really see,' said Scott, who finished in the twilight. 'I'm glad I got in, otherwise I would have an early start (Sunday) with a long wait in between.'
Stankowski praised the putting surfaces.
'The greens are phenomenal,' he said. 'The best greens we've putted on not only this year, but I can't remember better putting surfaces in my 14 years out here.'
Wagner's 64 broke the course record by one shot and included five consecutive birdies from No. 5 and seven during a nine-hole stretch.
'The guys on the course are going to chase me down today. It's the first time I've ever held a course record. It's exciting,' he said.
Wagner took command of the round on the front nine, taking a one-shot lead around the turn after making his fifth straight birdie on a 15-foot putt at No. 9. He knocked his 36-yard approach at No. 13 to within 2 feet to set up his last birdie and take a two-shot lead.
'I knew with no wind the course was going to play as easy as it has, and then I just really hit the ball solid and gave myself a lot of opportunities all day,' Wagner said.
Watson raced past him, though, with six birdies in seven holes beginning with a 5-foot putt at the 10th. He made a 9-foot birdie putt at the 12th, then made his fourth straight birdie at the 13th to move three ahead.
At the 15th, he knocked his 56-yard approach shot to 4 feet and posted another birdie ahead of the horn.
Defending champion Stuart Appleby was at 10 under with three holes remaining and alone in sixth place. Hunter Mahan and Bob Estes were on the course at 9 under, while Bernhard Langer (67) was in the Redstone clubhouse at 8 under.