ROCKFORD, Ill. (WTVO) — In the Stateline, we’ve already had more than a dozen tornadoes this spring. Nearly every county had a tornado touch down on March 31st. The Enhanced Fujita Scale rates tornadoes from a zero to five. It is exceptionally rare for EF5 tornadoes to occur, and it’s been a very long time since Illinois has seen one.

The Enhanced Fujita Scale is a damage scale used to rate tornado strength. It’s a combination of estimated wind speed and related damage.

Chicago National Weather Service Warning Coordination Meteorologist Mike Bardou says crews are sent out to survey damage once a tornado has passed, assigning an EF rating.

“There’s a whole range of potential damage that we look at that we use to determine and provide an estimated wind speed in what occurred with the tornado,” he said.

There are a lot of factors that go in what determine how long it can take to survey tornado damage.

“That’s a combination of a few things, it depends on what the weather is doing afterwards, so if we have more weather, we need staff here to work with the weather,” Bardou said. “If there’s just a lot of distance to cover, that certainly will take longer. Access to areas, are roads blocked, are trees blocking roads, that kind of thing, what’s closed down. And then sometimes we don’t find out about damage right away either and there may be areas that are affected that we may hear about even a couple days after the fact. So generally, for the more significant events, within a day or two at least. If it’s one or two maybe stronger tornadoes or one or two areas of damage, then it’s pretty straightforward to get that finished within a day or two. If it’s a lot of different areas, a lot of tornadoes, that can even take a week or two weeks to really finalize everything.”

The scale goes from an EF0, a weak tornado, up to an EF5, the most destructive. Anything EF2 or greater is “significant”.

EF0 tornadoes have wind speeds of 65-85 mph, while an EF5 tornado would be anything with winds greater than 200 mph.

EF0 tornadoes can cause minor damage to roofs and siding. EF1 damage is where a roof is severely stripped, homes can be overturned or damaged. In an EF2 roofs are torn off well-constructed homes and mobile homes can be destroyed. EF3 damage is where entire stories of well-constructed homes are destroyed and severe damage to large buildings. EF4 damage is when well-constructed houses and whole-framed homes are leveled. EF5 damage is when strong frame houses are leveled off foundations and swept away; high-rise buildings have significant structural deformation.

The last EF4 tornado in northern Illinois was the Fairdale-Rochelle tornado on April 9th, 2015. This tornado was on the ground for nearly 40 minutes. 22 people were injured and two people died.

The last F5 tornado in Illinois was more than 30 years ago, back in 1990, in Plainfield. This was before 2007 when the Enhanced Fujita Scale was just the Fujita Scale.

Although EF5 tornadoes are rare and only make up less than 1% of all tornadoes, it’s not a matter of fact if one is going to hit, it is when.

“Prepare for these things all the time. Especially in the spring as we go forward through the rest of the severe season, that’s been off to a quick start for us. Always prepare whether it’s lightning, wind, hail, or tornadoes.” Bardou said.

Having high weather awareness is key. “We’re still early in the season, so whether you’ve had your plan in place or now you’re thinking about what kind of a plan you need, make that plan. If you’ve got the plan, practice it. Know where you’re gonna be at the time of severe weather. Are you going to be at home? What does your plan look like at home? Where are your safe areas to go? The general rule is go to the lowest floor possible, put as many walls between you and the outside world as possible and as few windows. Even consider covering up with a blanket, or a pillow, or even putting some sort of helmet on your head.” Bardou said.

It is important to prepare and think of these events even when the weather is not active. When the weather is active, make sure to have several ways to get watches and warnings.