Along with sunny days, and 70-degree weather comes the start of tornado season.

The season lasts from April 1 to July 1, NIU staff meteorologist Gilbert Sebenste said.

“However, tornadoes have occurred in every month, at anytime during the year,” he said.

April to June is a peak time for tornadoes, with another minor peak from August to September, Sebenste said.

The Illinois state average for tornadoes is 26 per year, but for the past few years, the number of tornadoes to hit Illinois has more than doubled.

From 2002 to 2003, Illinois had more than 100 tornadoes, Sebenste said.

“Last year, we had 80 in the state, two of which came in sight of the university,” Sebenste said. “We got really lucky last year.”

Although Sebenste said it is impossible to predict, he said he thinks Illinois will see more than the average number of tornadoes again this year.

What causes a tornado is still unknown, but based on weather conditions, meteorologists can predict when there is a possibility for one.

First, warm, humid, unstable air is needed in addition to winds changing directions with height, Sebenste said.

Second, a warm or a cold front is also needed to lift the warm, moist air to produce a thunderstorm, he said.

“And if the wind shear is strong enough and the atmosphere unstable enough, you will get tornadoes,” Sebenste said. “But there is no set threshold. We’re still trying to figure that out.”

To ensure safety, officials said paying attention to the weather is key.

“Obviously, one of the important things in tornadoes is to be alert for the latest weather conditions,” said Mark Ratzer, a lead forecaster at the National Weather Service Forecast Office in Romeoville. “Tornadoes and thunderstorms develop and diminish quickly.”

In addition to watching the weather, having an emergency plan in place before a tornado hits is essential, Ratzer said.

“You want as many walls between you and a tornado as possible,” Ratzer said.

When a tornado warning is issued, people should take shelter in a basement, the lowest level of the building or in a small space with little or no windows, such as a bathroom or closet, he said.

For those on campus during severe weather, signs are posted with directions on where the nearest shelter is located.

These locations are also available online at www.weather.admin.niu.edu/bldgtorn2.html.

NIU students and staff are informed of severe weather by the National Weather Service through the 170 weather radios located on all NIU campuses, Sebenste said.

If a person is driving, Sebenste said to do the opposite of a commonly known myth – taking shelter under a bridge.

“They act as wind tunnels and further increase wind under the bridge,” he said. “They’re great for getting out of hail, but not for tornados.”

Instead, he suggests driving at right angles from the tornado or taking shelter in a ditch, as a last resort.