MAMMOTH LAKES – It appeared to be another serene, lazy morning at Crowley Lake. It was warm, cloudless, windless and bug-free. The famous trout-fishing lake on the Eastern Sierra was devoid of anglers, too. But Harry Blackburn knew better.

“When the midges hatch, the bite will turn on,” the veteran Eastern Sierra guide said.

And then Blackburn looked to the south.

“Thunderstorms are building,” he said, even though all that could be seen was one small puff of a cloud, probably somewhere over Bishop. “The wind’s going to come up, it’s going to get choppy.”

Three hours later, Blackburn was proven correct. The midges hatched and the trout were chasing his artificial lures. Cumulonimbus clouds, precursors to thunderstorms, were building to the south. Eventually, Blackburn hightailed it out of McGee Bay as the winds came up and the water began to get choppy.

A prophet? Hardly. As a guide for the newest fly-tackle store in Mammoth Lakes, Wilderness Outfitters Guide Service, Blackburn has had one day off from fishing this summer: the Fourth of July.

“Matching the hatch is the essence of fly-fishing,” he said. “I’m on the water all the time.”

Blackburn, reared in San Diego and on the East Coast, settled in the Eastern Sierra 15 years ago.

“I love fishing and hunting, and in this place, it’s all there in front of you. You have this huge outdoors area all in your back yard. This is the place to live. That’s why this place is so great.”

He hooked up with Mike Peters and they spent most of their free time float-tube fishing in McGee Bay. One day, they took a canoe to the area and began fly-fishing.

“I immediately said that I was going to get a boat and start guiding,” he recalls. “People thought I was crazy.”

Soon, all the other Eastern Sierra guides had boats, too. Blackburn, Peters, Lenny Yee and Tommy April formed the Eastside Guide Service and quickly found themselves busy nearly every day during the April-to-October trout season.

Last October, Mammoth Mountain, which has expanded its summer programs, decided it wanted to enter the fly-fishing business, too. The resort, which already offers an extensive mountain-biking program, hiking trails and rock climbing, enticed the fly-fishing company, Orvis, to open a shop.

“We’re diversifying our business,” Mammoth spokeswoman Joani Saari said. “We saw this as an opportunity to expand and Orvis was interested. There is a lot of fishing in this town.”

Blackburn, who coaches on the Mammoth Mountain junior ski program in the winter, jumped on board and so did his fellow Eastside Guide friends.

With Crowley into its annual artificial lures-only mode, Blackburn says the lake will start turning on with a tremendous bite. On a recent morning, he hit the Crowley grand slam, catching the Kamloops and Eagle Lake strain of rainbow trout and cutthroat and brown trout. With the wind too strong, he then helped an inexperienced fly angler catch half a dozen trout in the Wild Trout section of Hot Creek.

But Blackburn will fish more than just those two waters. He regularly takes anglers to the East Walker River, Twin Lakes Bridgeport, the June Lakes Loop, around the Mammoth lakes and the lower Owens River, too.