It was tough to tell who packed more of a punch at the 31st Mayor’s Cup, Kyle Suppa or Mother Nature?

Suppa torched Ala Wai for a 6-under-par 64 Saturday, birdieing six of the last seven holes. Nature nailed the normally arid municipal layout Sunday and Suppa carved a 66 around the day’s second deluge.

The Punahou senior, heading to the USC golf team in a year, won by seven over Moanalua senior Kyosuke Hara, who has verbally committed to Oregon State and shot 69 the final round.

They were the only golfers who broke par on a day that started bright and early at 6:30 a.m. The first group finished before 10 a.m. By then, the weather was not looking nearly as bright.

It took the leaders some six hours to slog through a course that eventually was besieged by casual water. Some golfers finished in bare feet. Suppa stopped to wring out his socks.

He still kept making putts.

Of his six back-nine birdies on Saturday, three came from outside 15 feet. The others were within 4 feet.

He took a four-shot advantage over Hara and Kamehameha graduate Justin Taparra — now a junior at Chaminade — into the final round.

Hara birdied Nos. 2 and 3 to cut his deficit in half. He bogeyed the par-3 fifth and Suppa birdied it to get his big lead back.

Game over.

Suppa would go bogey-free in the final round, draining three birdie putts on the first four holes of the back nine, when the rain was at its hardest.

“I was focusing on the rain more than anything on the back nine,” Suppa said. “That’s what happens when you are soaking wet.”

Added Hara: “It was downpouring so it was hard to be thinking about low scoring. It was dumping on us.”

Suppa didn’t think, he just kept making birdies. His winning score was the lowest since Rudy Cabalar shot 64-65 in 2012 — two years after this tournament was revived following a five-year absence.

“He hit quality shots, that’s for sure,” Hara said of Suppa. “He made up and down from wherever, which was unbeatable. He was awesome today. Like the first hole, his second shot hit a coconut tree. He was 40 yards out, chips it, makes the putt for par.”

Hara won the Mayor’s Cup two years ago. Last month, he and Suppa were selected to represent the U.S. at the inaugural Trans-Pacific Junior Golf Match in Beijing. The U.S./Mexico team won big (34.5-13.5) over the People’s Republic of China/Chinese Taipei. Suppa went 4-0-1 and Hara 3-2.

That was one of nearly 20 tournaments the two friends have each played this year, often with remarkable results. Suppa, the 2014 Hawaii State Golf Association Player of the Year, was in his first Sony Open in Hawaii this January.

He hopes it is not his last.

“It was a lot of fun playing in front of that kind of crowd,” said Suppa, whose family belongs to Waialae Country Club, “and against that kind of competition.”

Taparra closed with a 71 to claim third at 1-under 139. Shawn Lu (72) and Kengo Aoshima (74) tied for fourth at 142. Punahou’s Aiko Leong, the only woman in the field, shared 18th at 74—149.

Michael Wolfe (76—151) captured A flight. Jeff Irvine (77—152) and Marscel Lopez (80—158) won B and C. The Senior champion, decided just before dark, was Carl Ho (75—146) by a shot over Phil Anamizu (71).