The New Zealand golfer Danny Lee was four shots off the pace at the PGA championship in Wisconsin when the second round was suspended due to the threat of lightening.
Starting the day tied for third at four under for the championship, Lee picked hit one bogey on the 16th before being called back to the club house after birdies on the 2nd and the 4th.
Lee has five holes to play to complete his second round and was one under for the day despite falling into a tie for 12th at five under for the championship.
The Australians Jason Day and Matt Jones are leading at nine under par.
World number five Day, still seeking a first major title after several close calls, had completed 14 holes and Jones, 12.
Both players are five under for the round.
English world number six Justin Rose, the 2013 US Open champion, was a further stroke back with just one hole remaining.
Tied for Lee for 12th, the overnight leader Dustin Johnson was one over for the day at five under par with four holes left to play.
Jordan Spieth, once again delivered a special performance to surge into contention during a dramatic second round.
The Masters and U.S. Open champion, bidding to claim his third major title of the year and join an elite club, took advantage of relatively calm morning conditions at a sun-baked Whistling Straits by firing a five-under-par 67.
That left the young American ominously placed at six-under 138 with American Scott Piercy (70), just one stroke off the lead set by Swede David Lingmerth with half the field back in the clubhouse.
Lingmerth carded a roller-coaster 70 that included eight birdies on a day of low scoring for the early starters.
World number one Rory McIlroy, back in action to defend his PGA Championship crown after five weeks out due to an ankle injury, carded a second successive 71 to trail by five strokes.
"If anything, I'm probably just not as sharp with the short game as I'd like to be," McIlroy said after a round that included an eagle, just two birdies and a double-bogey at the tricky 18th, his ninth hole of the day.
"There's plenty of chances out here. I've been able to hit the driver as hard as I want, and I get around 18 holes easy."
Spieth, who had a 71 in tough afternoon conditions on Thursday when the wind was at its strongest, was delighted to play his way into contention.
"I feel good," he said. "I made a couple putts today. With a couple chip-ins for the week and really smart course management and good speed control, we have been able to hold ourselves in there."
South African George Coetzee put behind him missed cuts in his last three European Tour starts as he rocketed up the leaderboard with a sizzling 65 to finish at five under.
"I put some work in (on the range) last night and it paid off today," said Coetzee, who won two European Tour events earlier this year before losing form over the past three months.
Japan's Hiroshi Iwata also took advantage of the receptive conditions and flirted with the first 62 at a major before settling for a record-tying 63 in the second round.
Iwata, who racked up eight birdies, an eagle at the par-five 11th and a bogey, became the 25th player to shoot a 63 at a major as he vaulted within three shots of the lead.