"People think I'm crazy, but I was OK," she said.
"I don't like putting on a jacket when I've been hitting it well all day. I was just trying to keep the good things going."
By the time the gallery greeted Lewis on the 18th green she had finally relented and begrudgingly put on her rain jacket.
Minutes later, Lewis was warm and dried off in the clubhouse with a 12-under total that looked like it might stand up.
"I think it should be pretty good," Lewis said with the leaders still on the course.
Lewis ended up being one stroke short.
But being cold, wet and one stroke short of a trophy is still a good day for Lewis.
Not so long ago her dream of playing professional golf looked pretty far-fetched.
"There was a time when I was laying in a hospital bed and I couldn't sit up by myself," Lewis said. "Whether you are playing in the rain or whatever it is, I'm thankful for every day that I get out here."
Lewis was diagnosed with scoliosis -- an excessive rotation deformity of the spine -- at age 11. For 7 1/2 years she wore a back brace 18 hours a day, only taking it off to golf.
She was told that when she stopped growing she could lose the brace for good. After turning 18, she took off the brace but her condition continued to progress.
Just months after accepting a golf scholarship to the University of Arkansas, doctors told Lewis she needed surgery to prevent further damage to her back.
A rod and five screws were inserted into her spine and she was told not to bend or twist for six months. She couldn't even bend over to pick something off the floor, let alone swing a golf club.
Arkansas held a spot for Lewis and when she began to feel better she started to practise chipping and putting.
Eventually, in 2004, she was ready to report to the golf team.
Was the school ever glad to have her.
Over the next four years Lewis won 12 times, including the 2007 NCAA Division I championship.
She also won the 2007 Women's Southern Amateur and was named Golf Digest's Amateur of the Year.
"I play golf because I love to play. I got to school, got to college and played better," Lewis said. "My coach was like, 'You should give it a try, try to play as a professional.' "
So she tried.
Lewis turned professional in 2008. That year, she led the Women's U.S. Open after three rounds and went on to finish tied for third. She earned nearly $250,000 that season.
She joined the LPGA full time in 2009, finishing in the top 10 at the LPGA Championship before having her coming out party earlier this season at Mission Hills in California.
At the year's first major, the Kraft Nabisco Championship, Lewis entered the final round two shots back of world No. 1 Yani Tseng.
Tseng, who had won two of the past four majors, and Lewis, who had zero professional wins, made up the final pairing.
Lewis beat Tseng by five strokes that day to claim her first LPGA title -- and a major at that.
"This year has been awesome," Lewis said Sunday. "After winning, I didn't want to have a letdown, I didn't want to be the person that won the first major and then played horrible the rest of the year." Having far surpassed all of her goals for this season, Lewis had to make up some new ones.
"My goal for the rest of the year is, I actually went into the top 10 in the world rankings last week, so my goal is to stay there and finish top 5 on the money list."
Today's runner-up finish solidified both her top 10 status in the Rolex world rankings and her top 5 position on the LPGA money list.
It might be time for some new goals ... again.