SMITHS STATION, Ala. — As the sirens sounded Sunday afternoon, alerting residents just before deadly tornadoes cut through eastern Alabama, Terryn Smith, 12, and Hannah Mounce, 13, immediately sprung to action.

“When the sirens went off, that’s when we took cover,” Terryn told NBC News.

The girls hid with Terryn’s mother and a friend in a Lee County home, huddled with pillows and blankets on the floor of the kitchen, a windowless room in the center of the house.

Krista Smith, Terryn’s mother, shielded the girls with her body as windows blew out and doors slammed in other parts of the home.

“I was like scared that the house would take off and we weren’t going to make it,” Hannah said.

The tornadoes roared through Lee County on Sunday afternoon, killing at least 23 people, including multiple children, in what a local official called “the worst natural disaster that has ever occurred” in the county.

A tornado watch for Lee County was issued at 11:40 a.m. CST (12:40 p.m. ET), with the first tornado warning issued at 1:58 p.m. CST. That warning was issued just five minutes before the first damage report in the county.

It was one of the deadliest tornado events in the state since 2011, when more than 230 people across Alabama were killed that April.

The 2011 tornado outbreak left about 300 dead throughout the southeastern United States. In response, the National Weather Service improved its operations for helping communities prepare for natural disasters, said Douglas Hilderbrand, a meteorologist who leads the NWS’ Weather-Ready National Ambassador program. The initiative began in response to that tornado season.

“That April 2011 experience was really an eye-opener for the National Weather Service, in the sense that it was a very well forecast event … we were highlighting the magnitude of this event days in advance and yet 300 people lost their lives,” he said.

“It really shined a light on how there’s much more that needs to be done from a National Weather Service perspective, but also a community perspective in terms of working together,” he said.

The NWS invested in its technology and services to not only issue timely and more accurate tornado warnings but also to disseminate information to the community, he said.

The NWS recommends having multiple ways to receive warnings about extreme weather, such as receiving phone alerts, and warnings on television broadcasts and the National Oceanic and Atmospheric Administration’s Weather Radio.

During a news conference Monday, Lee County Emergency Management Director Kathy Carson said she was “pretty sure” the sirens sounded warnings ahead of the tornado, but that both the weather service and the agency were increasingly reliant on sending targeted cellphone alerts to residents about tornadoes.

The 2011 outbreak in Alabama was declared a federal emergency and led to improvements in the state’s tornado shelters in addition to its warning systems, experts said.

“Since then, through funds from FEMA, there has been a lot of work to put in community safe rooms to be used during storms, as well as money that has gone out through individual mitigation funds to put in tornado safe rooms in houses,” said Lisa McCormick, an expert on emergency preparedness and associate dean for public health practice at the University of Alabama at Birmingham.

McCormick said the state also worked to upgrade its outdoor warning systems so that they would be able to target county areas being impacted by incoming storms.

Experts recommend having a plan long before a tornado threat occurs, such as going to a basement, storm cellar or interior room away from windows and outside walls. People in mobile homes are encouraged to evacuate to community shelters.

Myles Tatum, a Lee County resident, said he and his two sons, ages 7 and 10, ran and hid inside a closet in their barn after they saw a tornado heading toward them.

He said what was going through his mind as he heard the tornado coming was, the "same thing we're supposed to do, that's what they teach us -- go find cover in the best place you can find."

Tatum said they could not get the door of the closet closed and just hoped the roof would not rip off. In the end, he and his boys survived.

"The only reason this part of the barn was here, I'm convinced, is the Lord saved us," he said.

"We just piled up on top of everything, there's no time to worry about anything else, right? It's what we're supposed to do," he said.