Shane Lowry got off to a lightning start in the second round of the US PGA only to see his charge up the leaderboard halted by an electrical storm that washed out play for the rest of the day.

The Offaly man (31) played beautifully for his first ten holes at Bellerive Country Club, picking up shots at the 12th, 13th and 17th before saving par brilliantly from 13 feet at the 18th.

Three-under for the day, he was tied for 16th on four-under-par, just six shots behind clubhouse leader Gary Woodland, when the hooter sounded as he prepared to tee off on the second, his 11th.

Rory McIlroy was treading water, level par for the day and struggling badly with his wedges.

Denied on the greens, he was sitting perilously on the projected level par cut line after seven holes with playing partner Tiger Woods three-under for the day in a tie for 23rd.

Pádraig Harrington remained where he started the day, tied for 75th on one-over after making one birdie and one bogey in his first six holes.

Greystones Paul Dunne — ranked last in the 156-man field for driving accuracy— was four-over for the championship through six holes after following a double bogey at the short 13th with a birdie at the next.

American Rickie Fowler, who opened with a 65 on Thursday, picked up two shots in his first 10 holes to move up to tied fourth on seven-under.

The morning was marked by red-hot scoring with Brooks Koepka and Charl Schwartzel taking advantage of receptive conditions to equal the lowest round in PGA Championship history with seven-under-par 63s.

Overnight leader Woodland shot 66 to take a one-shot lead over Kevin Kisner (64)  with Koepka alone in third on eight-under after lipping out for what would have been a major championship record equalling 62.

World number one Dustin Johnson (66), Schwartzel (63), Thomas Pieters (65) and Fowler were tied for fourth on seven-under with South African Brandon Stone solo eighth on six-under after a 68.

Jordan Spieth keeping his chances of the career Grand Slam alive with a scrambling, four-under-par 66 moving him up to tied 23rd on three-under.

Despite his struggles, he confessed that he'd still prefer a tougher, firmer conditions.

"You can just fire in and you get away with more — you don't have to be as precise," Spieth said. 

"That's frustrating in a major championship because typically what it does is you don't really have to be as precise on and around the greens. That's frustrating to me because I feel like that's an advantage that I have."