As the line of windy squalls passed out over Lake Michigan that hot June morning 40 years ago, Joseph Pecararo assumed the worst of the day's weather was over.

The sky was clear and the lake was still by the time the 24-year-old lifeguard captain arrived for work at North Avenue beach.

With temperatures expected to climb to nearly 100, he expected a big Saturday crowd.

But so far the beach was deserted, except for a pair of fishermen out on the hook-shaped pier and a line of rowboats stored in front of the beachhouse, ready for use in an emergency.

They turned out to be of no use at all against the silent killer racing toward the beach from the southeast that morning: a freakish, 10-foot-high inland tidal wave that would sweep eight anglers to death and pound the Lake Michigan shoreline all the way from the Chicago River to Wilmette on its way into the history books.

"The water came up suddenly and our boats began to float," remembers Pecararo, now general superintendent of beaches for the Chicago Park District.

"We ran out and went to pull the boats up and when we did, there was a wave."

The wall of water crashed over the lifeguards without warning, knocking them from their feet. When they surfaced, "we laughed, we thought it was kind of funny," he remembers.

"But seconds later a person came running over and said there was a fisherman swept off the pier," Pecararo said. John Jaworski, fishing with his 18-year-old son Joseph, had disappeared.

Jaworski was just the first of the victims of one of Lake Michigan's most unusual phenomena: the seiche.

Such potentially deadly waves, the worst of which hit Chicago on June 26, 1954, are formed when a squall line with high winds drives water across the lake, in the same way that blowing on a hot cup of coffee pushes the liquid toward the far rim. The winds then pass off the lake, but the water sloshes back across, producing damaging waves with no storm to warn of their impending arrival.

That morning, the seiche-producing storm started in LaCrosse, Wis., and moved southeasterly through Madison, Rockford and Milwaukee. At 7:30 a.m. it crossed over Chicago and blew out onto Lake Michigan at nearly 55 miles an hour.

At 8:10 a.m. it hit Michigan City, pushing a 5-foot wall of water over the breakwater and onto the shore. It then reflected back and began racing toward Chicago, where it crashed with terrifying fury an hour and 20 minutes later.

Unlike anglers in Michigan City, who fled the squall for higher ground, the Chicago fishermen had no storm to warn them of the deadly wave racing their way.

The only warning Herbert Riederer, then a 24-year-old state conservation officer, had of the impending wave was a wet shoe. He'd just finished writing a ticket to a fisherman without a license when water suddenly rose onto the Montrose Harbor breakwater where he was standing.

"I stepped up to higher ground," he remembers. "As I did, I heard a rush of water, and when I looked back, I saw people being washed off the pier."

"It's not something you can forget," he said. "I can still see that woman, she was riding the crest of this huge wave into the harbor mouth, then she disappeared."

Mae Gabriel, 48, and her husband, Edward, 49, were later found drowned.

Riederer, who had no radio, raced for help to a nearby roadway, where he "commandeered the first car I saw and had him drive me to the bait shop" a half-mile away, where the nearest phone was located.

Soon Montrose Harbor was crawling with divers, including the lifeguards from North Avenue Beach. They had just managed to recover Jaworski's body in the rough water by forming a line and pushing it in toward the shore when a squad car rolled up with the news: "Dozens down at Montrose!"

"We jumped in the squad car. It was a wild ride," Pecararo remembers.

Three bodies were pulled from the harbor that morning; four more were recovered later. One was Theodore Stempinski, the man Riederer, who is no longer with the conservation service, had issued the ticket. He had apparently stopped to pick up his fishing gear before fleeing the pier.

The deadly seiche triggered a flurry of scientific study into the phenomenon that quickly saved lives: Just weeks later, on July 6, 1954, a similar storm passed over Chicago, prompting the local weather service to issue a seiche warning.

When the seiche hit, waters rushed into the Loyola beach parking lot and up the steps of the North Avenue beachhouse, then raced away. But the beaches had been cleared and no one was hurt.

Since the 1954 disaster so-called seiche fences have been installed on many breakwaters. The simple metal cables and posts anchored in concrete are intended to provide a handhold in the event of a sudden wave.

Large seiches remain relatively rare. Over the last 100 years, weather watchers have recorded about 10 major ones on Lake Michigan. Last year three seiche warnings were issued for Chicago, none for waves approaching the size of those in 1954, Pecararo said.

"We never saw anything like that," Pecararo remembers. "I thought the end of the world was coming."