A series of severe storms triggered tornado warnings and tornado watches in much of central and northern Illinois on March 19, moving out of the area by late evening. The storms caused a smattering of power outages in northwest Indiana and widespread damage across the Chicagoland area.

Illinois residents only have a few weeks before tornado season officially kicks off, so here's a guide to prepare for incoming storms.

When is tornado season?

Nearly 80% of all tornadoes occur between April 1 and June 30 in Illinois, according to the National Weather Service. In recent years, however, half of the state's tornadoes have taken place in the fall or winter.

The state typically experiences about 50 tornadoes per year.

Tornado terminology explained

The NWS explains the difference between the varying tornado alert terminology on its website.

A tornado watch means tornadoes are possible in the area, while a tornado warning means a twister has been sighted or indicated by the weather radar. A tornado emergency is the most severe alert, meaning a violent tornado has touched down in the area.

The website uses the phrases "be prepared," "take action" and "seek shelter immediately" to summarize the three alerts.

What do tornado sirens mean?

Sirens are tested on the first Tuesday of each month at 10 a.m. in Illinois. The state uses a single alert siren to signify an emergency alert, such as a severe storm or tornado warning.

An audio sample of this siren is available on the Illinois Emergency Management Agency website, along with a sample of the rising and falling tone used to signify a homeland security or attack emergency.

How to plan for tornadoes

What to do in the event of a tornado

Those who are home should go to an interior room without windows, making sure not to forget family or pets. Groups at work or school should follow pre-determined tornado drills, making sure to stay away from large open rooms, such as cafeterias and gymnasiums.

Individuals outside should quickly proceed to sturdy, safe buildings, avoiding sheds, storage facilities, mobile homes and tents. Avoid being in a vehicle during a tornado by driving to the nearest shelter or abandoning your car to seek shelter in a low-lying area, such as a ditch or ravine. If you're unable to leave your vehicle, get down in your car and cover your head.

What does it mean when the sky turns green?

Experts told Accuweather there is no direct correlation between green skies and oncoming tornadoes.

Penn State University meteorology professor Craig Bohren explained that the spectrum of direct sunlight is shifted from blue to a perceived red, yellow and orange as the sun sets in the sky. When this light is transmitted by thick clouds composed of water droplets and ice particles, "the results are a green sky."