With his second consecutive 5-under 65, Kuchar was at 10-under 130. DeLaet completed his second-round 67, even with three consecutive bogeys, before a two-hour weather delay just after noon Friday.
Kuchar was among 54 players who were unable to finish Friday night after play was suspended because of an approaching storm that brought heavy rain and lightning. Conditions were calm for the resumption of play.
Kuchar, No. 13 in the world and the highest-ranked player in the field, was on the green at the par-3 16th to start Saturday, and two-putted from about 40 feet for par.
Kuchar took the lead with a 6-foot-birdie putt at the 457-yard 14th hole on Friday, and recovered from a drive into a fairway bunker on the 15th for a par while clouds darkened and thunder could be heard in the distance.
Soon after Kuchar, the WGC-Accenture Match Play winner in February, teed off at the par-3 16th, and his ball landed about 40 feet from the cup, the horn sounded ending play. It was raining heavily about 30 minutes later.
First-round leader Ryan Palmer, the Colonial member who had an opening 62, was still at 8 under after an up-and-down 12 holes Friday that he managed to play at even par.
Flesch's 64 matched the best completed round of the day and, more importantly, will end his string of 16 missed cuts on the PGA Tour since October 2011.
The 2004 Colonial champion missed the cut in all 12 of his PGA Tour starts last year before right shoulder surgery in August, and is playing only his third tour event this year. The 45-year-old Flesch is playing on a non-exempt major medical extension and has to make $647,510 between this weekend and his next three events to prolong that medical extension.
"I'm very comfortable here and just glad to actually play on the weekend now," Flesch said. "I was actually cruising, then I got that rain delay and I kind of lost all of my rhythm. ... It's like starting your whole round over. My swing didn't feel very well on those last three (holes)."
Flesch was on the course trying to complete his morning round when play was stopped for the first time. He had just made a 33-foot birdie putt at the difficult par-4 fifth hole, his 14th hole of the day. The lefty finished with four pars in a row.
Palmer hit his opening drive way right at No. 1, a par 5 that is generally among Colonial's easiest holes, and started with a par. The former Texas A&M golfer with three PGA Tour wins sank an 11-foot birdie putt at No. 3, but hit his drive at No. 5 out of bounds and had to drop in the rough, leading a double bogey. He followed with a bogey at No. 6 after driving into a fairway bunker.
In his last three holes before the suspension of play, Palmer made an 8-foot birdied at No. 10 and rolled in a 27-footer at No. 12. He never teed off at the par-3 13th.
"When you shoot 8 under, it's hard to come back sometimes. ... I was calm all day, confident," Palmer said. "Now I' even par sitting on 13th tee, I have soft greens and pretty calm winds in the morning, so maybe I can get up there with Kuchar and we can have some fun tomorrow."
Kuchar matched DeLaet for the lead after four birdies his first seven holes. Kuchar had a 15-foot eagle chance at No. 1 that came up just short, then hit is approach at No. 2 that stopped inside 3 feet after ricocheting out of the cup.
"The front nine, I really got it going," Kuchar said. "I jarred a shot on 2 that landed in the hole and came back out. ... I really got off to a great start. And then I kept playing some good golf."
DeLaet was 10 under after his third consecutive birdie, a 6-footer at the 373-yard second hole that was his shortest putt in that stretch. Then he arrived at Colonial's famed "horrible horseshoe" as the Nos. 3-5 holes are known because of their layout and the difficulty of the stretch -- a 239-yard par 3 sandwiched by the two longest par 4s on the course.
"It definitely got me today," said DeLaet, who bogeyed all three holes.
After DeLaet's tee shot at the 470-yard third hole went into a fairway bunker, the Canadian badly missed the green at the par 3 before his approach shot at the 475-yard fifth hole came up short of the green. But DeLaet finished strong, with consecutive birdies to finish after he had come up just short of a 31-foot birdie at No. 7.
"Always nice, and kind of got myself right back in it," said DeLaet, whose has never finished better than third on the PGA Tour in 69 events. "The main thing for me, I feel more comfortable now if I see my name on the leaderboard. ... A few years ago, if I was in 15th going into the weekend, I knew if I could just maintain that position that that would be a 'good check' kind of thing. My mindset now is beyond that. I want to try to win golf tournaments."