OTTAWA -- Former prime minister Brian Mulroney predicts Donald Trump's unprecedented diatribe against Justin Trudeau is a passing storm.

Mulroney, who has a personal relationship with Trump and has been quietly advising the prime minister on how to deal with the mercurial U.S. president, likened Trump's weekend tirade to "serious summer squalls."

"They come upon you abruptly and they dissipate just as quickly," he said Monday.

"I think it's serious but because it's serious doesn't mean it's lethal."

Trump unleashed a Twitter harangue about Trudeau after departing the G7 summit in Quebec on Saturday, miffed that the Canadian prime minister had reiterated during a closing news conference that Canada intends to impose counter-tariffs on some American goods in retaliation for "insulting" tariffs imposed by Trump against Canadian steel and aluminum imports -- which the president has justified on national security grounds.

Trudeau had been saying the same thing for several weeks, but Trump apparently found it reprehensible to repeat the message on the eve of his historic summit with North Korean dictator Kim Jong-un.

Trump called Trudeau "very dishonest and weak," among other things. And on Sunday, two of his top aides took to the talk show circuit to pile on.

Chief trade adviser Peter Navarro said there's "a special place in hell" for Trudeau and anyone else who negotiates in "bad faith" with Trump. And chief economic adviser Larry Kudlow accused Trudeau of betrayal and stabbing Trump in the back.

"I've never seen language like this, least of all from subordinates of the president directed at the prime minister of their greatest friend and ally," Mulroney said.

"This I've never seen before. Nor has anybody else."

Mulroney said he thought Trudeau's closing remarks were "fairly benign and certainly didn't warrant any attack."

"All Mr. Trudeau was doing, in a rather gentle way, was articulating the position of his government, which would be the position of any Canadian government in these circumstances," he said, adding that the counter-tariffs make sense.

"In this business, somebody puts a tariff on your products, you put a tariff on theirs. Now, how it's received on the other side is something else, but that's life."

Trudeau has so far not commented on Trump's tirade. Foreign Affairs Minister Chrystia Freeland was measured Sunday, saying only that "Canada does not believe that ad hominem attacks are a particularly appropriate or useful way to conduct our relations with other countries."

Mulroney said the government is right not to trade insults with Trump.

"We shouldn't engage with these things. You can't win that kind of a contest."