But a severe thunderstorm predicted to hit Thursday afternoon could bring more lightning than the US Golf Association (USGA) really wanted to see when world number one Woods, McIlroy and Scott tee off at 1:14 p.m. (1714 GMT).
A course that has already soaked up 6.5 inches of rain in four days has enjoyed two dry practice days but forecasters expect up to three inches of rain on Thursday with severe conditions including a flash flood watch.
“There could be some really high winds with us, potentially damaging winds, even some hail,” USGA executive director Mike Davis said. “It depends on really what hits us or how lucky or unlucky we are.”
The course figures to be jammed with spectators watching the feature trio of 14-time major champion Woods, seeking his first major crown since the 2008 US Open, second-ranked McIlroy, the 2011 US Open winner, and third-ranked Adam Scott, the reigning Masters champion from Australia.
“Some energy and electricity, playing with him at any time,” Scott said. “And given the hype around this grouping and being a major, it’s going to be an intense couple of days.”
Sunny skies are expected the next three days but an already-saturated course figures to produce less of a challenge in the year’s second major championship with greens holding more approach shots, although dense rough remains a threat.
Mud clinging to golf balls in another worry with no lift, clean and place rules being used as players would normally have in PGA Tour events.
“We wouldn’t be adopting that rule this week,” USGA championship committee chairman Tom O’Toole said. “And if it was so bad, then the obvious response to that, or consequence, would be we probably wouldn’t be playing.”
But US veteran Steve Stricker warned that mudballs could decide a winner and 2010 US Open champion Graeme McDowell echoed that notion.
“Mud balls are a problem. I think they’re unfair… it literally can cost you shots,” McDowell said.
“When it bakes and tops a little bit, there are going to be a lot of mud balls. I hope they make the right call. If it’s picking up mud then I think we need to lift, clean and place just for a level playing field.”
A field of 156 players from 21 nations will compete over the 6,996-yard layout where Bobby Jones completed a 1930 sweep of the US and British Opens and Amateurs and Ben Hogan won the 1950 US Open after a near-fatal auto accident.
Woods, chasing the all-time record 18 majors won by Jack Nicklaus, seeks a fourth US Open crown after 2000, 2002 and 2008 titles to match the all-time record shared by Nicklaus, Hogan, Jones and Willie Anderson.
“I would like to obviously put my name there at the end of the week,” Woods said. “But I’ve got to do my work and put myself there.”
Woods, 37, has won four times this year, giving him 78 career PGA titles, four shy of the late Sam Snead’s all-time record. He expects mudballs could be a factor by Sunday as well.
“We haven’t dealt with teeing it up in a tournament yet with it raining and drying out for a couple of days and the mudballs appearing,” Woods said. “That is going to be interesting, especially the longer holes.”
Phil Mickelson, a five-time US Open runner-up longing to finally capture the only American major that has eluded him, has a Thursday morning 7:11 start after flying across the United States hours earlier to attend his daughter Amanda’s eighth-grade graduation, missing two days of practice at Merion.
Amanda is the same child whose impending birth in 1999 had Mickelson’s caddie carrying a pager at the US Open at Pinehurst in case his wife went into labor so he could leave and be with his wife. Mickelson finished second.
“I’ll be ready on Thursday,” Mickelson said.
Merion offers front-loaded birdie chances on a mix of long and short holes, including two par-5 sin the first four holes and a 115-yard par-3 13th, but the final five formidable holes will have players clawing to avert bogeys or worse.
“You have to hang on for dear life those last five holes,” McDowell said. “I can’t think of a tougher finish that I’ve seen at a US Open.”
“Once you get to 14 it’s going to be tough to make birdies,” Woods said.