For much of a Thursday that offered a harsh reminder of Shinnecock Hills’ capacity for chaos, the US Open leaderboard was as congested as County Road 39 at the start of a Hamptons weekend, a gridlocked mass of contenders separated by little more than one or two shots. Then Wyndham Clark found another gear, roaring clear of the traffic to open a shocking four-stroke lead before darkness brought the first round to a halt.

Clark, the 2023 champion, was six under par through 16 holes when the horn blew and play was suspended at 8.25pm, holding a commanding advantage over a chasing group at two-under that included the clubhouse leader Sam Stevens. Four other players were also at two-under with holes remaining, while nine more – including Masters champion Rory McIlroy – sat at one-under.

For much of the afternoon, a pair of 21-year-old amateur Oklahoma college golfers were among the surprise names near the top. One was Ryder Cowan, a rising senior at Oklahoma playing in his first US Open after surviving a three-for-two playoff at final qualifying in Florida to claim the last spot in the 156-man field. The other was Oklahoma State standout Preston Stout, the world’s second-ranked amateur. Both spent time in a share of the lead before slipping back into the pack.

That’s around when Clark found the open lane. The 32-year-old American took full advantage of unexpectedly benign conditions during the golden hour, reeling off birdie, birdie and eagle at the third, fourth and fifth holes to transform a crowded scoreboard into one with rare separation. No player has led the US Open by four shots or more after the opening round since Tommy Armour carried a five-shot advantage into the second day in 1933.

“Everything was kind of clicking,” said Clark, who said this week he’s out for redemption after smashing a locker at Oakmont after a missed cut at last year’s event. “We were definitely fortunate with the wind laying down.”

All week long the conversation at Shinnecock, the hallowed Long Island track hosting America’s national championship for a sixth time, had centred on gusts strong enough to send approach shots careering across fairways and force the USGA into unusual measures to ensure the course remained a fair test. Instead, a dense cloak that swallowed much of the course shortly after dawn prompted the first fog delay during the first round of a US Open since Torrey Pines five years ago.

Visibility began to deteriorate not long after local qualifier James Nicholas struck the opening tee shot of the championship into the grey at 6.35am. Half an hour later, officials suspended play as a dense soupy coastal haze engulfed Shinnecock Hills, obscuring fairways and greens and bringing the opening round to a standstill. The delay lasted just over two hours before play resumed shortly after 9am, all but ensuring the round would extend into Friday.

McIlroy wasted little time announcing himself after the restart. The Northern Irishman rolled in birdie putts at the 11th and 12th to reach two under par and briefly claim the solo lead, continuing a rich run of US Open form that has yielded six top-10 finishes and two runner-up finishes in his past seven appearances.

That consistency can be traced to his last visit to Shinnecock in 2018, when he opened with rounds of 80 and 70 and missed the cut. “I remember thinking to myself, I’ve got this backwards,” McIlroy said. “I should be in my comfort zone at Shinnecock and not here.” The disappointment, he explained after Thursday’s round, inspired him to retool his game around the major championships, prioritising trajectory control, wedge play and short-game precision.

The world No 2 later climbed into the solo lead at three under with an eagle at the fifth – his first at a US Open in nine years – after reaching the green with a pitching wedge from 194 yards. Two late bogeys dropped McIlroy back to a one-under 69, but left him firmly in contention heading into Friday.

The morning gloom soon gave way to a windswept afternoon on the sprawling, treeless 7,440-yard course less than a mile from the Atlantic Ocean, where Scottie Scheffler’s first crack at completing the career grand slam hit early turbulence as he dropped six strokes adrift of the pace before battling for a two-over 72 to remain within striking distance.

“Overall it was a really challenging day,” Scheffler said. “If you told me when I was staring at my par putt on nine that I would post two-over today, I would definitely have taken it at the time.”

Shinnecock’s unsparing history suggests almost nobody is out of it yet. The venue has also proven atypically forgiving of poor starts: two of the three US Open champions since 1980 to open with 75 or worse did so at the course, with Raymond Floyd recovering in 1986 and Brooks Koepka repeating the feat in 2018.

With blustery winds exceeding 30mph threatening to tip the balance from challenging to punitive, the USGA is taking the rare step of watering and misting greens during the opening two rounds. The goal is to keep the course’s notoriously devilish putting surfaces from drying out and becoming excessively quick. The approach appeared to have the backing of the players. Scheffler said the greens were softer than he expected, but suggested tournament officials had little choice given the forecast.

“I think the last thing that they wanted was having balls blowing off greens,” he said. “They might have put a little extra juice on them last night to slow them down.”