Whoever said lightning never strikes twice hasn’t beheld the 553-metre lightning rod that is the CN Tower.
Canada’s tallest structure is also the city’s biggest lightning target, especially in summer. Photos shared on Twitter showed the tower was licked again during Monday night’s storm.
Because of its height and slim structure, lightning hits the tower scores of times a year, according to Ali Hussein, an electrical engineering professor at Ryerson University who has studied lightning for nearly three decades.
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“The closeness of a charged cloud, which usually carries (a) negative charge at its bottom, causes the creation of an extremely high electric field in the vicinity of a tall structure’s top,” he explained in an email.
Usually, the CN Tower is struck 75 to 80 times per year, said Geoffrey Coulson, an Environment Canada meteorologist.
But some days, it’s pummeled. On Aug. 24, 2011, for example, it was mercilessly zapped 52 times in only 84 minutes, Hussein said.
That’s the equivalent of one strike every 97 seconds, he pointed out. “This is probably a world record.”
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That doesn’t mean visitors or staff have anything to worry about. The tower channels the charge through long copper strips running from the top of its radio and cell antennae down to 52 buried grounding rods.
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Irene Knight, the tower’s manager of public relations, said “a lightning strike is not discernible to anyone inside the CN Tower. The sky may flash white for an instant. It is most visible outside and away from the tower.”
Monico Santiago, who has worked at the tower for two years, says being inside during a thunderstorm can be a thrill. He was in the SkyPod, 447 meters above the ground, one stormy day when lightning struck and he heard “a large cracking sound.”
“It’s just deafening … There’s a loud boom, then it’s silent for a few seconds. “I was more excited than anything else just because, when you’re up there, it’s a different experience.”
The CN Tower has withstood most lightning strikes without incident — but for at least one notable exception.
On May 6, 1976 — a little more than a month before the tower opened to the public — lightning struck 12 metres from the top, causing $25,000 in damage and destroying 21-inch thick fiberglass moulds.
“It hit a spot where lightning normally doesn’t hit,” the CN Tower’s director of design and construction, Malachy Grant, told the Star at the time. “It was a freak lightning strike.”
