Play was suspended for the day with the plan to resume play at 7am local time (1pm Irish) on Saturday.

Day and Jones have four and six holes respectively to complete in their second rounds but will sleep on a one-shot shared lead over England's Justin Rose, who was playing his final hole when the hooter sounded to call play to a halt.

Sweden's David Lingmerth is the clubhouse leader, having earlier shot a two-under-par 70 to complete his 36 holes in seven under par with Americans Harris English and Tony Finau at the same mark but still to finish. They are one ahead of Jordan Spieth (67), whose second round play was much admired by his playing partner Rory McIlroy.

A frustrated McIlroy failed to make inroads into the PGA Championship lead as the world number one continued his comeback from a ruptured ankle ligament in solid if unspectacular style in Wisconsin on Friday. He carded a second consecutive one-under-par 71 as playing partner Spieth beat the Irishman by four strokes to move to a shot back from clubhouse leader David Lingmerth of Sweden.

It was a day, in much more favourable conditions, which also saw Japan's Hiroshi Iwata fire a nine-under par 63 featuring an eagle three at the par-five 11th, eight birdies and a single bogey. That matched the major championship record low round of 24 others, including McIlroy, whose round had come at St Andrews in 2010.

"I have seen these media center's on TV. I wanted to be interviewed." Hiroshi Iwata, after his 63. #PGAChamp pic.twitter.com/dQHSAlKlU7

— PGA Championship (@PGAChampionship) August 14, 2015

Five years on and with temperatures reaching above 30c on the Lake Michigan shoreline, McIlroy did not struggle but his misfiring putter and an iron game that he said lacked the sharpness of round one was compounded by his proximity to the man who can replace him at the top of the rankings making steady progress towards a third major title of the year.

Spieth, 22, had six birdies and one bogey in his five-under 67 to get to six under for the tournament after Lingmerth posted a 70 to reach seven under with overnight leader Dustin Johnson among the late starters from six under.

McIlroy lies five behind Lingmerth, still in the hunt to retain the title he won last year at Valhalla, but more impressed with Spieth than his own putting.

“I always thought this course... suited the longer hitters, and it does to some degree,” McIlroy said. “But I feel like there's a lot of ways to get around this golf course.

“Jordan showed that over the last couple of days. He hasn't hit the ball miles, he hits it far enough, he's definitely above average in terms of length. But he's the prime example of someone whose game is very efficient, when he gives himself chances. Especially today he took them, and then when he got out of position he was able to get it up and down.

“I felt like I played good in parts; drove the ball pretty well again. Maybe my iron play wasn't quite as good as it was yesterday and the greens that I did miss I wasn't very sharp around the greens. You're going to do that, you're going to miss greens around here. You're going to have to have more of a short game to be able to salvage par sometimes. I wasn't quite able to do that today at points. But there's still enough good stuff to give me encouragement and make me feel that I can shoot a low one tomorrow and get myself back into it.”

McIlroy, 26, reported no discomfort from his left ankle after his second competitive round back following a football injury suffered on July 4. Yet the R word did rear its head.

“I don't know if it's rust or I just didn't putt well. I don't really want to blame it on rust. But I didn't putt as well as I would have liked. So, yeah, maybe just work on that a little bit before I tee off tomorrow and it would be great to hole a few more putts, because I feel like I'm giving myself plenty of chances.

“That was probably one of the most surprising things about yesterday is how quickly I got back into the mindset of tournament golf and being aggressive. So that was a nice surprise in some ways. That hasn't really been an issue, it's just being a bit more efficient, whenever you give yourself chances, take them, and be able to get it up and down when you put yourself out of position.

“I felt like I played better than what the score reflected. A little bit annoyed... I felt like I should have got that ball up and down on 7. And then I had a great chance on 8 for birdie and didn't take that. A couple of days in a row where I haven't finished the round of golf the way I wanted to. I'm not annoyed, I don't feel that I should be annoyed, but just a little more disappointed with how I finished.”

Lingmerth was sitting in the clubhouse on seven under, a shot ahead of Spieth and Scott Piercy (70), but the Swede did not expect, correctly as it turned out, that to last too long.

“A very good feeling,” Lingmerth said of his round before adding, “but there's some scores to be had out there and I think my lead will probably not last too long.

“I feel like someone will probably outdo me by a couple shots here today, at least. But obviously I'll hopefully be within reach after today and really looking forward to the next few days.”