OAKMONT, Pa. — So much for those dreams of a firm, fast U.S. Open at Oakmont.

Nearly a half-inch of rain fell during a Wednesday afternoon thunderstorm that also scattered tree limbs and twigs across fairways. But crews were out as soon as the rain stopped, and officials hope the course won't play significantly different today.

Speed of the greens should be the same, said Tim Moraghan, the U.S. Golf Association's agronomist, but firmness could be affected.

"It's not going to be what we planned for," Moraghan said. "Things were moving along quite well (before the storm). We thought we'd have a true, hard test for players on Thursday. The rain has altered this a little bit."

It had been about a week since any significant rainfall in the Pittsburgh area, allowing the course to play as firm and fast as expected for a U.S. Open. With the weekend forecast calling for clear skies and warm temperatures, the greens were expected to firm up even more.