Olympia Fields found itself firming up in the grasp of the heat wave that was crippling the heart of the country. With heat indices in the mid 90s and stifling humidity, low scores were at a premium, with only Jutanugarn and Jung recording sub-par rounds.

However, Jutanugarn found the heat and humidity just to her liking, and reminiscent of her home in Bangkok, where she lives most of the year.

“I love hot weather because in Thailand, it’s hotter than here,” said Jutanugarn, who competed in the 2011 U.S. Women’s Open at The Broadmoor in Colorado Springs, Colo.

Jutanugarn, whose summer has also included a victory at the Rolex Girls Junior Championship and a runner-up finish at the Rolex Tournament of Champions, opened as hot as the temperature, recording four birdies in her opening five holes.

“Five holes at four under was very good,” she said with a smile of her early-round performance.

Along with the weather, more comfort came to Jutanugarn in the form of a familiar face carrying her golf bag – her older sister, Moriya. Moriya Jutanugarn, who tied for 32nd at the Women’s Open and claimed low-amateur honors, was forced to withdraw from the Girls’ Junior due to a nagging wrist injury. However, with father Somboon watching his girls from a distance, Moriya and Ariya formed a formidable team.

“She made me feel like I can do it,” said Ariya Jutanugarn of her caddie sister. “With my putting, she read the lies so good. She kept my yardage to my approach shots so good.”

Jung’s round played the total opposite to Jutanugarn’s. While Jutanugarn opened hot and cooled through her round, the 17-year-old Jung quickly found herself at two over after three holes. However, she was able to get her game back on track with a birdie at the par-5 fourth hole.

“I birdied that one after making two straight bogeys, so I kind of got back into it,” said Jung, who will attend Duke University in the fall. “After that, I hit the ball really solid and putted very well.

“My putter was really awesome today, and I was driving it long and straight for most of the time. It was a really good round.”

Four players sit at even-par 72, including 15-year-old Katelyn Reynolds of Los Angeles. She came out of the gate neck-and-neck with Jutanugarn, opening with three consecutive birdies. However, a bogey-double bogey turn ultimately dropped her into a tie for third.

“I started off really well with a really long putt and I just built on that,” said Reynolds, who is competing in her first USGA championship. “But I hit a couple snags. I hit a couple drives to the right that I kind of had to punch out a couple of times.”

Joining Reynolds at even par were Jisoo Keel, 15, of Canada; Kaitlin Park, 17, of Tustin Ranch, Calif.; and Mariko Tumangan, 17, of San Jose, Calif.

Competing in her fifth U.S. Girls’ Junior, Tumangan was the picture of consistency in her morning round. She opened with a birdie on the par-4 10th hole, her first hole of the day. After evening her score with a bogey on par-4 17th, the Stanford commitment saved her share of the lead with a clutch putt on her final hole, the par-4 ninth.

“I hit a pretty good drive and I chunked my eight iron,” said Tumangan. “It was supposed to go about 140 [yards] and it went about 110. I chipped it onto the green and I had a 15-foot left-to-right putt and I sunk it. That was pretty good.”

Park also cruised through the morning’s brutal weather to even-par 72.

“The whole day today was just really consistent,” said Park, who lost in the first round of match play at the 2010 championship. “I had all these pars, and I had one bogey on the front and I finished off with a birdie. My dad clapped so much on the last hole because he was like, ‘When is this birdie going to come!’”

Eleven players were five strokes behind Jutanugarn at 1-over 73, including 2011 U.S. Women’s Open competitors Mariel Galdiano, 13, of Pearl City, Hawaii, and Gabriella Then, 15, of Rancho Cucamonga, Calif., and 2010 Girls’ Junior quarterfinalist Stephanie Liu, 14, of St. Louis, Mo.

It was a tough Monday for the two past Girls’ Junior runners-up in the field, with neither player able to build any momentum. Katelyn Dambaugh, 16, of Goose Creek, S.C., the runner-up in 2010, carded six bogeys and shot 6-over 78, while 2008 runner-up Karen Chung, 17, of Livingston, N.J., recorded five bogeys for a 5-over 77.

The 2011 U.S. Girls’ Junior will continue with the second round of stroke-play qualifying on Tuesday. Following stroke play, the 156-player field will be trimmed to 64 for match play, with the championship scheduled to be decided in a 36-hole final on Saturday.

The U.S. Girls’ Junior is one of 13 championships conducted annually by the United States Golf Association, 10 of which are strictly for amateurs.

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