At 4:30 p.m. Sunday, thunder rumbled over Congressional Country Club, and the couple of dozen players who were finishing up practice for the U.S. Open heeded the warning of a horn atop the clubhouse and scampered for cover. The reaction among club and tournament officials: joy.

“We need this rain to be a good soaking,” said Paul Klinedinst, co-chair of Congressional’s U.S. Open committee.

By all accounts, Congressional is ready to host the Open — which begins Thursday and runs through Sunday — for the third time. But Washington has been dealing with exceptionally warm weather over the past two weeks, and that has impacted the rough. Mike Giuffre, the director of golf course maintenance, believes one rain will bring the rough back to life, making it a big more gnarly.

Though staffers from the United States Golf Association, which stages the Open, and contractors were due to be working through Sunday night, the club and the course are prepared.

“It’s coming down to the final minute for them,” Klinedinst said. “But it’s gone really well. The preparations are unbelievable.”

Construction of what amounts to a small city — merchandise tents, corporate suites, grandstands, concessions, etc. — began in mid-March. Workers were finishing the construction of spectator gates and painting even late Sunday afternoon.

Among those who got in at least nine holes of practice Sunday were K.J. Choi, who won the AT&T National at Congressional in 2007; Bubba Watson, a three-time winner on tour over the past year; Australian Aaron Baddeley, who played with Watson. Monday’s practice rounds begin with a group of young stars — Jason Day, Nick Watney, Justin Rose and Webb Simpson — signed up to tee off at 7 a.m. from No. 10.

The USGA announced that tickets to all four rounds of competition are sold out. Tickets for practice rounds Monday, Tuesday and Wednesday are available at the main and clubhouse admission gates. Children 12 and under will be admitted for free during any day of the tournament when accompanied by an adult ticket holder.

“I think we’re where we want to be,” Kinedinst said.

Caddie for a week

Adam Scott finished his second practice round in as many days with Steve Williams, Tiger Woods’s regular caddie, carrying his bag, and he reiterated what Woods’s camp said Saturday: This is a one-week arrangement.

“Steve knew I was in between guys,” Scott said, “and we’ve talked a lot over the years. Anyway, when Tiger had to withdraw, I called him to check if he was available for the week. That’s what he’s doing, and I’m really grateful he’s doing it.”

Everything regarding Woods, though, ends up being a big deal. The 14-time major champion won’t be at Congressional because of lingering issues with his left knee and Achilles’ tendon, and Scott is looking for a permanent caddie. Scott said Williams, who has not worked for anyone other than Woods since they paired up in 1999, called his boss.

“He checked it all out with Tiger,” Scott said. “It’s just for the week. It’s no big deal. But I’m very grateful to both of them for that chance while I’m still looking for a guy full-time. . . . Hopefully I can use his experience late on Sunday. That would be great.”

Local knowledge

Perhaps no one in the 156-player field is dealing with more pre-tournament requests than Mike “Fluff” Cowan, the caddie for 2003 Open champion Jim Furyk.

“I’m doing what I can,” Cowan said, “and if it ain’t enough, it ain’t enough.”

Cowan, a Maine native, lives in Potomac and is a member at Congressional. When the PGA Tour makes stops at the club, Cowan has downplayed his knowledge of the layout as a factor in how Furyk performs. “I know how to get from the ninth green to the 10th tee,” he said. “But beyond that . . . ”

When the Open was last held at Congressional, Cowan carried Woods’s bag. He has been with Furyk since 1999.

“It’s always been an important tournament for me,” Cowan said. “The fact that it’s played in what has become my hometown at a golf course that I play my golf at, yeah, it’s a little different.”

Byrd joins the field

Zack Byrd of Myrtle Beach, S.C., gained entry into the field Sunday evening. Byrd, an alternate from a qualifying tournament in Summit, N.J., took one of the three spots the USGA was holding because the winner of the PGA Tour event this week, the FedEx St. Jude Classic — Harrison Frazar — was already in the field. A spot was held in case the winner in Memphis won for the second time in the past year and had not yet qualified for the Open. The final two players in the field, both alternates from sectional qualifying sites, will be announced Monday morning.