OKLAHOMA CITY | Last year’s tornado season wasn’t the worst in Oklahoma history, either in the number of twisters or the number of lives taken.But the deadly barrage that killed more than 30 people scared Oklahomans in a way that previous storms had not, moving them to add tornado shelters or reinforced safe rooms to their homes.There’s just one problem: The surge of interest in tornado safety has overwhelmed companies that build the shelters, creating long waiting lists and forcing many people to endure the most dangerous part of this season without any added protection.“Pretty much anywhere you go right now, the soonest anyone can install is about mid-June,” said Kayli Phillips, who works in sales and accounting at Norman-based Thunderground Storm Shelters. “We’re booked solid until then.”Thunderground, which opened about two years ago, is part of a booming new industry that has taken shape as more Americans seek to shield their families from severe weather. The demand intensified last year following the series of deadly twisters in central Oklahoma, where a single tornado on May 20, 2013, killed 24 people and destroyed 1,100 homes in Moore.Since then, Moore residents have added about 1,100 basements or shelters, according to city spokeswoman Deidre Ebrey. In all, the city has an estimated 6,000 shelters or basements.In nearby Oklahoma City, more than 8,000 storm shelter permits have been issued since May 2013, according to Kristy Yager, a spokeswoman for Oklahoma City. In 2009, just 322 permits were issued.The 2013 tornadoes “pretty much kept us booked up the entire year,” Phillips said.Abby Brown, a sales manager for Edmond, Oklahoma-based GFS Storm Shelters, said there’s always a waiting list for installations, but it generally peaks starting in March, when people begin thinking about the upcoming storm season. The company, which has been in business for four years, installs about 175 shelters a month.“People are thinking about it more. People who have lived in Oklahoma all their lives sometimes may not have ever thought that they needed a storm shelter until last year,” she said.Oklahoma is not the only state where families are confronting their twister fears.After a half-mile-wide tornado hit the Little Rock suburb of Vilonia last month, officials said the death toll of 15 could have been worse if residents had not piled into underground shelters and fortified safe rooms.Alisa Smith, sales manager for Austin, Arkansas-based Tornado Shelters Systems, said the company is working around the clock to keep up with demand. Sales have doubled since last year, to about 300 shelters. New customers have to wait six to eight weeks for installation, she said.“I think this tornado scared a lot of mothers,” she said. “There were two little boys lost in the Vilonia storm, so I think a lot of mothers are saying, ‘Forget those granite counter tops or sunroom, let’s put in a shelter.’”It’s not unusual for an episode of severe weather to send demand soaring, said Ernst Kiesling, executive director of the National Storm Shelter Association.Just as parts of the central U.S. are seeing an increase now, the South experienced a similar trend in 2011, after twisters killed more than 300, he said.But the shelters and safe rooms don’t come cheap. Pricing is based on a variety of factors, including size, location within the home and the type of door used. The priciest models can cost as much as $14,000. Smaller ones can be had for a few thousand dollars.Some people turn to a lottery-style federal program that provides matching money for residential shelters. The government offers rebates of up to $2,000 per home. About 10,000 people or families apply annually for one of about 500 rebates, said Keli Cain, spokeswoman for the Oklahoma Department of Emergency Management. Other cities and towns may offer their own rebate programs.Jennifer Sweeten and her husband used a refund from their federal taxes to install a shelter in their Oklahoma City home in March 2013.“I thought: How stupid are we to live in Oklahoma without a storm shelter or basement?” Sweeten said. “We felt like that was the best use of our refund. My husband actually wanted to go on a little vacation, and I said, ‘Nope, we’re getting a storm shelter.’”It’s lucky they did. Two months later, two tornadoes swept through the area, and the family took shelter underground.“It gives me great security,” Sweeten said. “I felt like we were prepared, and we were safe and that was worth great peace of mind.”Prior to last May’s storms, only one neighbor had a storm shelter, Sweeten said. Since then, four more have installed them.Tessa Beaulieu, of Edmond, Oklahoma, made sure the new home she is building with her husband had a shelter. She ordered the shelter in January, and it was installed at the end of April.“We have three small children,” Beaulieu said. “So obviously protecting them and us is a top priority.”Associated Press Writer Sean Murphy contributed to this report.Follow Kristi Eaton on Twitter at https://twitter.com/KristiEaton .Copyright 2014 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.