Welshman Jamie Donaldson continued to impress in only the second Major Championship he has ever played in America.
Last month's Irish Open champion - his first European Tour win in 255 starts - started the US PGA Championship with a three under par 69 and when he set off again with a birdie this morning he was up into a tie for fifth place.
Swede Carl Pettersson led overnight at six under and was among the second round's later starters, as was Rory McIlroy following his 67.
Among those looking to make a move on another relatively calm morning were Alex Noren, Graeme McDowell, Justin Rose, Padraig Harrington, Paul Lawrie and Luke Donald.
Noren was best placed after coming home in a three under 33 last night for a 67, and the Swede parred the opening hole of his second round.
McDowell stood four under, Rose three under, Harrington two under, Lawrie one over and World Number One Donald two over after going in the lake and taking a double-bogey five at the short 17th last night.
The halfway cut was expected to fall at around one over, although much depended on whether the wind picked up later in the day. Thunderstorms were also in the forecast.
It was not long before the wind did gather strength and among those to have problems was Spain's Gonzalo Fernandez-Castaño.
In a blow to his hopes of staying in contention, and improving his chances of a Ryder Cup debut, he fell from five under to two under with four bogeys - and a birdie - in his first five holes.
Donaldson remained four under after five holes, but Adam Scott, trying to hit back from the shock of losing last month's Open with four closing bogeys, dropped a stroke at the 412 yard 12th to be three under.
As that remained the first weather warning notice of the day was posted around the course, although play continued for the time being.
Donaldson added another birdie at the 480 yard par four sixth and moved into joint second place just one behind Pettersson.
Neither Rose nor Donald made good starts, the former bogeying the 447 yard tenth to be two under and Donald double-bogeying it to stand four over and in danger of missing the cut just like he did at the US Open Championship.
