CHATTANOOGA (WRCB) -- Beth Vargas and her two small children take advantage of Thursday's unusually warm weather by visiting Coolidge Park.

"We moved here from Florida, so we'll take days like this any day," says Vargas as she laughs.

But the beauty of late February sunshine, puffy clouds and temperatures in the 70s can turn ugly if the right ingredients combine.

Mix the warmth with enough atmospheric moisture, then throw in a front to help lift the air and a thunderstorm is born. If enough energy builds, the storm turns severe.

"It makes us nervous," says Vargas.

The National Weather Service classifies a storm as severe if it produces straight-line winds of 58 miles per hour or higher, hail an inch in diameter or greater, or a tornado.

Straight-line winds can be as destructive as a twister. And after last April's deadly outbreak, local retailers saw spikes in sales of weather alert radios.

"After the storm we pretty much sold out and we ordered more," recalls Kyle Burriss of Ace Hardware in Red Bank.

Burriss is trying to keep up with the demand. His sales immediately increased three to four fold compared to the months leading up to the event.

"We sold probably 16 to 18 weather radios after the storm happened to maybe 3, 4, or 5 before," says Burriss.

He says sales remained steady through the summer.

As Channel 3 has reminded you for years, it's best to prepare before severe weather strikes by purchasing a radio.

Vargas reluctantly admits her procrastination, perhaps because her town of Dalton, Georgia escaped major damage.

"That feeling that it's not going to happen to us, or it already happened right near us, now it's somewhere else's turn," says Vargas.

But with her family to protect she's having a change of heart. The radio's instant alerts could save their lives one day.

"It would be a good idea," Vargas says. "I guess I better talk to my husband about it."

Severe thunderstorms also produce dangerous lighting and sometimes flash flooding.

For more information on severe weather preparedness visit the National Weather Service online.

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