Winless since claiming this very title four years ago, Day backed up his opening seven-under 63 with a round of three-under 67 as the rain set in at TPC Potomac at Avenel Farm.

His two-round total of 10-under puts him three shots clear of playing partner the first two days, Max Homa (66), followed a shot further back by Denny McCarthy (69), Luke List (66), Kurt Kitayama (67) and James Hahn (68).

The wet weather is expected to continue into the weekend and to be at its worse on Saturday, putting Day in the frame of mind to grind out a long-awaited win.

“I’ve always kind of liked US Open formats in regards to how tough the golf course is. You kind of have to grind it out,” Day said.

“Typically, when you have tough conditions, long golf courses, tough conditions, thick rough, the guys that are playing well, they kind of usually find their way towards the top.

“It’s nice to be able to get in at 10-under through two rounds, especially with what kind of weather we’ve got coming in on the weekend.

“I’m looking forward to it. It’s nice to be back in the mix, nice to be leading.

“It’s still two more days left, so I can’t get too far ahead of myself.”

Adamant that he has come a long way in terms of confidence in his swing and his putting stroke since finishing one stroke out of the playoff at the Farmers Insurance Open in January, Day explained the difficulty that the conditions presented.

“I felt like I had maybe a handful of 4-irons and 5-irons out there today and luckily enough I hit the majority of those close,” said Day, who dispensed off his customary cap after nine holes due to water dripping from the brim.

“When you have conditions like this, it’s really hard to commit to a shot because you’re going in there and you’re doing it kind of a lot quicker than your normal pre-shot routine. You have to force yourself to hit the shot and trust that.

“Some of the iron shots that went left today, just a little quick in the transition, didn’t kind of wait for it. I kind of worked it out and found my way on the back side.”

Day is the lone Aussie to advance to the weekend with Cam Davis (75), Cameron Percy (72), Marc Leishman (75), Brett Drewitt (72), Matt Jones (72), Aaron Baddeley (84) all over par on day two.

Despite a second round of one-over 73 Kiwi Ryan Fox remains in contention at the Betfred British Masters as he chases his second DP World Tour title of the year.

He will start the third round four behind Germany’s Hurly Long, Jason Scrivener (74) the only Australian to make the cut.