Honestly, most well-made park benches are not going to tip over in a routine storm. But “storm” covers a lot of ground. A 40 mph gust is very different from 80 mph hurricane-force wind, and a heavy cast-iron bench bolted to a concrete pad is very different from a lightweight aluminum bench sitting on soft grass.
The biggest factors are weight, footprint, anchor method, and wind exposure. A typical commercial park bench weighs anywhere from 80 to 250+ pounds. That mass alone resists tipping in normal winds, but if the bench is not anchored, a strong gust can still slide or flip it once wind gets underneath the seat or backrest. Benches with open slat gaps tend to shed wind better than solid panels, but any bench can become a sail in extreme conditions.
Here is what actually keeps a bench in place in high winds:
Ground anchoring: Bolting legs to a concrete pad or using ground spikes/anchors is the single most effective upgrade. A properly bolted six-foot bench can handle most severe thunderstorms without moving.
Weight and material: Cast iron and heavy steel resist tipping more than aluminum or recycled plastic. However, even heavy benches can shift if they are not fixed to the ground.
Footprint and design: A wider stance, lower center of gravity, and perforated seat/back reduce wind leverage. Benches with a solid backrest catch more wind.
Location: Benches placed on exposed hilltops, piers, or coastal paths face much higher wind loads than benches tucked near buildings or trees.
For most parks and backyards, a bench that is either heavy enough or anchored to the ground should stay put in a typical storm. If you live in a hurricane-prone or tornado-prone area, no outdoor bench is guaranteed safe. Bring portable furniture inside or secure it to a rated anchor. My rule of thumb: if you can lift one end easily, it needs to be anchored.