After a tornado zigzagged through a shady campground in early March in Iowa’s Red Haw State Park, a visitor had been killed — his camper destroyed. The tornado, which was an EF-3 on the 0 to 5 Enhanced Fujita scale for intensity, also injured a man who had been living year-round in his RV at the privately owned Country Cabins Motel and RV Park. It crushed his camper, damaged nearby cabins and toppled several large trees.

Recreational vehicles, or RVs, aren’t anchored to the ground, making the structures on wheels a dangerous place to be in a storm: They can flip in strong winds or slip away in floods.

Amid a decades-long surge in the sales and use of RVs, which soared further since the start of the pandemic, millions of Americans will be traveling and sleeping in these mobile structures this year. Camping enthusiasts, especially those new to the hobby, may not realize the risks when severe weather strikes.

Manufactured homes — formerly called mobile or trailer homes — and homes without basements are anchored to the ground, while campers and RVs are not, said Valerie Sanders, a meteorologist whose business, WeatherCall Services, sells alert systems to help campers more accurately pinpoint the proximity of severe weather. Manufactured homes, if anchored based on government codes established after Hurricane Andrew, are as safe as most structures in tornadoes up to EF-3, Sanders said.

“A camper or RV has no such restrictions,” she said, calling them the “single most vulnerable thing you can live in.”

In June 2010, 20 campers, including eight children, died when the Little Missouri River rose more than 20 feet within hours. The banks overflowed and swept away RVs and their occupants in Albert Pike Recreation Area in Arkansas.

“A lot of people don’t think about flooding,” said Pat Spoden, an avid camper who is a meteorologist with the National Weather Service in Paducah, Ky. “You might be in a campground in a little valley, alongside this quiet little stream, but depending where that stream comes from, it doesn’t even have to rain on top of you, it can rain a few miles downstream and suddenly a wall of water comes by and it can sweep the camper away.”

“It’s not a rare occurrence,” said Chad Kelchen, park supervisor at Red Haw State Park. “I have seen even a seven-inch rain, on a flat campground, wipe things out.”

Meteorologists worry that with the increasing number of campers, more deaths and injuries are likely.

“It’s a ticking bomb,” Sanders said. “There’s going to be some major mass casualty in a campground that is weather-related and it’s going to be front-page national news.”

More than 11 million Americans own an RV, according to the RV Industry Association, and many more rent them for vacations. RVs range from small “pop-up” campers to large “motor homes.”

“The RV industry has experienced long-term growth for 40 years, but we definitely have seen interest become supercharged in the past two years,” RVIA spokeswoman Monika Geraci said.

Geraci said there’s also been a demographic shift in buyers. The median age for RV owners is 53, but that drops to 33 when looking at people who bought RVs for the first time last year, she said.

While campsites are everywhere, the biggest draw is America’s more-than-400 national parks, Geraci said.

Visits were already soaring pre-pandemic. This February, the National Park Service reported a renewed boom, with visits jumping by 60 million over 2020 after the pandemic closed down park facilities for much of the year.

State parks are seeing similar surges. In Iowa, state park and forest visits were up by 24 percent in 2021 compared with 2018, with over 3 million added visitors; overnight camping rose by more than 230,000, or 31 percent, said Tammie Krausman of the Iowa Department of Natural Resources.

The surge in camping also means popular campgrounds are booked months in advance, making last-minute changes stressful, Geraci said.

Overbooking of campsites has also become a sensitive issue, according to RV blogs and online forums. RV users report that campers, as well as automated “bots,” are hoarding spots. When campsite spots are fully booked, it can make it harder for visitors to switch their plans if faced with concerning weather.

National parks offer refunds if they close campgrounds due to inclement weather, said NPS spokeswoman Cynthia Hernandez. Otherwise, there is normally a $10 fee for modifying or canceling a reservation.

A spokesman for the National Association of RV Parks and Campgrounds declined to discuss campground fees and cancellation policies at privately owned sites.

Still, Sanders says the danger of imminent severe weather should overshadow the stress of lost reservations.

“By the time the watches come out, pack up and get out of Dodge,” she said.

When there are winds of 60, 70 or even 100 mph during a storm, “you don’t want to stay in your RV,” Spoden said.

“Most campgrounds have a brick or cinder block bathroom that you can get into any time of the day or night,” Spoden said. “You need to know where that is and how to get there in the middle of the night.”

That March 5 tornado “touched down in the middle of the campground like a ton of bricks,” Kelchen said. It destroyed multiple open picnic shelters, while a brick building containing showers for campers was largely unscathed, losing only some roof shingles.

“If the name of the park is ‘Something-something Cave State Park,’ well, head to the cave,” Sanders said.

“Never try to drive an RV in high winds,” said Dave Titley, a retired meteorologist who has taken up camping in a “bumper-pulled” Airstream RV in the past three years. “Remember, an RV is not a tornado shelter, even though during ‘normal strong’ winds of 30-40 mph, it feels secure compared with a tent. I’ve seen RVs, which are often made of lightweight fiberglass — rolling over in 60 mph winds.”

Titley recommends seeking a roadside rest stop, truck stop or any commercial building: “Just get off the road.”

A key to safe camping is staying alert to weather forecasts.

“We always recommend using multiple means of obtaining weather information,” said Christine Wielgos, an NWS meteorologist whose office serves southeastern Missouri, southern Illinois, western Kentucky and southwestern Indiana. One option is a battery-operated NOAA weather radio, which is available at hardware stores and big-box retailers and needs to be programmed for specific counties. While NOAA radios cover much of the United States, transmitter signals can be poor in some rugged areas.

For campers with internet service on cellphones or laptops, weather.gov has a continuously updated interactive map and posts regular updates on social media. Titley offers similar guidance for campers at RV Weather, a weather safety site he created in 2021.

“The beauty of RVing is that they are on wheels,” Geraci said. “Stay informed and if there is bad weather, use those wheels and avoid that weather in the first place.”

Hernandez suggested having a backup plan in place, and knowing “when it is time to move to Plan B.”