The idea that tornadoes are magnetically attracted to mobile home parks is almost a morbid joke in the United States—a way to cope with the predictable horror of seeing these vulnerable communities destroyed year after year, killing and injuring dozens of people. Mobile homes, commonly known as trailers, are so frequently destroyed in bad storms that it almost seems like these structures are targeted for destruction by tornadoes. The factoid is somewhat true, but for the wrong reasons.

A map showing the tracks of every recorded tornado in the United States between 1950 and 2015. Map: Dennis Mersereau

The United States averages about 1000 tornadoes every year. Most of those tornadoes touch down in the central and southern parts of the country, but they can and do happen in all 50 states. A huge majority of tornadoes—80 percent, in fact—don’t cause too much damage and wind up on the lower end of the Enhanced Fujita Scale, which is used to estimate a tornado’s winds based on the damage it produces.

Most structures can stand up against the winds of a small tornado. Not without damage, of course, but if you’re in a well-built home or office building, you have good odds of coming out of an EF-1 tornado with four walls and most of a roof dangling above you. Mobile homes are much different.

A map showing the percentage of mobile homes in each county and parish in the United States. Map: Dennis Mersereau

A significant percentage of homes in rural parts of the United States are mobile homes. The number of residences that are mobile homes is greater than 10 percent in many parts of the South, the West, and around the Appalachian Mountains. The number of mobile homes in the South is particularly concerning when you overlay historical tornado tracks on the above map.

All recorded tornado tracks between 1950 and 2015 overlain on top of the percentage of mobile homes by county. Map: Dennis Mersereau

Here we get to the crux of the issue. Tornadoes don’t go out of their way to hit mobile homes—you’re just more likely to live in one of these homes if you live in places where tornadoes are common. Compounding the issue is the fact that mobile homes simply aren’t built to withstand the winds of a bad thunderstorm, let alone a tornado. A huge part of tornado safety relies on the sturdiness of the building that takes a direct hit. Many mobile homes are built with cheaper construction materials that aren’t rated to withstand a fraction of the winds of a sturdier structure.

Tucked away in the guidelines that the National Weather Service uses to estimate the strength of tornadoes are their estimates for how strong a tornado’s winds have to be to destroy a standard, single-wide mobile home. According to their scale, it only takes winds of about 87 mph to shift a mobile home off its blocks. Winds of 89 mph are sufficient to peel the roof off the home. The entire mobile home begins to flip over and roll downwind once a tornado’s wind speed climbs up around 98 mph. The whole building is destroyed once winds exceed 100 mph.

Those destructive 100 mph winds would make a tornado rated an EF-1, which is on average the most common rating for tornadoes in the country. But 20 percent of all tornadoes that touch down are stronger than that, and many of them occur in regions where lots of people live in mobile homes. Compare that to the damage a single-family home would sustain in the same tornado: broken windows, a busted garage door, a broken chimney, and some roof damage. It’s a far cry from losing everything (and possibly everyone) you know and love. That’s the terrifying reality that many people face each spring and summer, and it’s why mobile homes are so frequently damaged in destructive storms.