Earlier Thursday, Xue Chen and Zhang Xi won China's first beach volleyball medal, beating Brazilians Talita and Renata 21-19, 21-17 for the bronze.
Walsh put an early end to China's chances to add a gold when she quick-hit May-Treanor's pass between Wang and Tian. The Americans dropped to their knees on the wet sand, hugging each other before shaking hands with the officials and running to the stands to embrace their friends and families.
They were still celebrating, wrapping themselves in U.S. flags, as organizers worked through the rain to set up the podium for the medal ceremony.
Walsh is nicknamed "Six Feet of Sunshine," but even her bubbly California smile and cheerleaders' demeanor couldn't part the clouds that drenched the Chaoyang Park venue for the bronze- and gold-medal matches. It was no day to be at the beach - not for Wang and Tian, and not for the fans who huddled under pastel ponchos and umbrellas that, on a day more appropriate for sun and sand, would be used as parasols.
But the 12,200-seat venue was packed, the dancers in bikinis jiggled to rock music and the players pressed on without concern for the weather. The wet and heavy ball forced them to bump-set instead of doing it over their heads, and the sometimes driving rain made it difficult to look up to receive passes.
"When the ball goes too high, you can't see it too easy," said Renata, her eyes wet from crying, as well. "But it's OK, because if it is raining for us, it is raining for them."
The Americans scored three straight points to break a 17-all tie in the first. China survived one set point before May-Treanor spiked one down the line for the winner.
The Americans cruised through the two-year qualifying process in a year, giving Walsh a break this spring to recover from offseason shoulder surgery. Managing the pain with massages and a special tape that is said to increase blood flow, Walsh showed no signs of wear.
Tian did need a medical time-out with the score 17-15. As she sat under the canopy that covers the bench, a trainer massaged her left arm briefly before sending her back to the sand.