(CBS) — The National Weather Service says the tornado that swept through Ottawa and Naplate yesterday was an EF-3 – with winds of 155 miles an hour.

Working with the National Weather Service — as their teams go through LaSalle County — is Dr. Victor Gensini, professor of meteorology at the College of DuPage.

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“These types of systems are not uncommon in the spring. I think what probably strikes us most interestingly is the fact that this happened in February, late February.  It’s a little early to be getting into severe weather season, but all the ingredients were in place,” he says.

Gensini says the tornado was its most intense in Naplate at the Pilkington Glass plant.

And on what’s called the Fujita Scale — rating the intensity of tornadoes from zero to 5 – the tornado at its most intense was an EF-3, he says, traveling at about 155 mph.

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Gensini says the belief that tornadoes don’t cross rivers is an urban legend.

He says this tornado not only crossed the Illinois River, it straddled it for awhile.

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