The first round had one delay of two hours, 16 minutes and later a second delay eventually halted play for the day at Warwick Hills Golf and Country Club. The first round will resume at 8:00 a.m. (ET) on Friday with the second round to follow.
World No. 1 Tiger Woods carded a 6-under-par 66 and shares sixth place with Arron Oberholser. Woods is coming off winning his third British Open crown, while Oberholser won for the first time earlier this year at the Pebble Beach National Pro-Am.
Woods, the 2002 champion, played the back nine first on Thursday and ran off five straight birdies from the 10th to open his round. He parred the next four, then birdied the par-5 first to move to minus-6.
'It's awfully fun when that happens,' Woods said of his early birdie run. 'I did start off on the easier of the two sides though and got it going early. I just couldn't quite keep it going.'
The 30-year-old posted five straight pars from the second. Woods birdied the par-5 seventh to get within two of Weir, but stumbled to a bogey on the eighth to end three back.
Weir collected a birdie on the third to open his round. He came right back with a birdie on the fourth. The Canadian posted birdies on seven and nine to make the turn at minus-4.
The 2003 Masters champion caught fire on the second nine. Weir birdied the par-5 13th, then sank a birdie try at 14. He made it three in a row as his birdie putt at the 15th found the bottom of the cup.
Weir was not done either. At the par-5 16th, Weir collected his eighth birdie. He made it five birdies in a row at 17 to get to minus-9 and parred the last for the lead.
Singh, like Woods, started on the 10th tee Thursday, but he parred the first three holes. After that, Singh birdied four straight from the 13th.
The Fijian, who missed the cut at the British Open, got to minus-6 with birdies on one and three. He stumbled to a bogey at the par-4 fourth. Singh reclaimed that lost stroke with a birdie at the sixth.
Singh, the only three-time Buick Open winner, made it two straight as he birdied the par-5 seventh. The world No. 3 birdied the par-4 ninth to gain second place before weather halted play for the day.
'I just played well today, and made some nice putts to get it going,' Singh stated. 'Momentum is good, plus it's pretty soft so you can go for the flags and not have to worry about bouncing it over.'
Lucas Glover, Robert Allenby and Vaughn Taylor share eighth place at 5-under-par 67.
Kris Cox, Steve Lowery, David McKenzie, Sean O'Hair and Scott Verplank are one stroke further back at minus-4. They were joined there by Jeffery Overton, who was playing the 18th when play was stopped for the day.