A sustained wind speed of 70 miles per hour (MPH) represents a severe weather event. This velocity corresponds to a Force 11 designation (Violent Storm) on the Beaufort Scale, associated with widespread damage and often encountered during the minimum sustained speeds of a Category 1 hurricane. Whether a car can be moved by this force depends on the complex interaction between the wind’s power and the vehicle’s physical properties. Analyzing this dynamic involves understanding the physics of wind pressure and the counteracting forces of friction and mass.
The Force of 70 MPH Wind
The force exerted by wind increases exponentially, not linearly, with velocity. A 70 MPH wind generates a dynamic pressure of approximately 12.5 pounds per square foot (psf) on a perpendicular surface. To find the total lateral force, this pressure is multiplied by the car’s exposed surface area and drag coefficient. For a typical mid-sized sedan with a 50 square foot side profile, the total wind load might exceed 600 pounds.
This lateral force must be compared against the static friction holding the vehicle in place. A standard 3,000-pound sedan requires roughly 2,700 pounds of lateral force to overcome static friction on dry pavement and initiate a slide. Since the 70 MPH wind force is significantly less than this threshold, a parked passenger car on dry ground is generally stable. However, the risk increases dramatically for lighter vehicles, those parked on wet or icy surfaces, or those subject to sudden, higher-velocity gusts. The wind force also creates a twisting motion that can destabilize the vehicle, especially when the center of pressure is high relative to the ground.
Vehicle Characteristics That Influence Stability
Vehicle stability against high winds is determined by specific design characteristics.
Mass and Friction
Mass is a primary factor; a heavier car increases the downward force on the tires, which increases the static friction required for lateral movement. Lighter vehicles, such as small hatchbacks, offer less resistance to the wind load and can be pushed more easily.
Profile and Center of Gravity
Vehicles with a large, flat surface area and a high center of gravity, such as cargo vans, recreational vehicles, or large SUVs, present a greater target for the wind. This increased surface area means the 12.5 psf pressure is applied over a larger area, significantly increasing the net lateral force. The higher center of gravity also makes these vehicles far more susceptible to rolling over than lower-profile sedans.
Tire Contact
The contact between the tires and the ground provides the final resistance. When parked, the main counter-force is static friction, though applying the emergency brake and turning the wheels toward the curb slightly increases resistance. If the vehicle is in motion, high wind can overwhelm the lateral force the tires generate, causing the car to veer sharply or slide uncontrollably.
Secondary Damage Risks Beyond Movement
Even if a stationary vehicle is too heavy to be pushed by a 70 MPH wind, it is highly vulnerable to extensive external damage. Winds classified as a Violent Storm cause widespread structural damage and uproot trees. The greatest danger comes from airborne debris, such as tree limbs, roofing shingles, street signs, and construction materials.
These fast-moving objects can dent body panels, shatter glass, and cause significant damage. Power lines are often brought down, posing a fatal hazard if they fall onto or near the vehicle. For drivers traveling in these conditions, risks include the loss of vehicle control, as a sudden gust can cause a car to momentarily veer, increasing the probability of collision.
What to Do When Winds Reach 70 MPH
The most effective strategy when wind speeds are forecast to reach 70 MPH is to avoid driving entirely. If travel is unavoidable, reducing speed allows the driver to compensate for sudden sideways pushes. Maintain a firm, two-handed grip on the steering wheel and keep extra distance from other vehicles, especially high-sided trucks or trailers, which can be blown off course.
Protecting Parked Vehicles
Strategic placement is the best defense against damage for parked vehicles:
- Park inside a garage or under a secure, load-bearing structure for the highest protection from flying debris.
- If parking outdoors, place the vehicle as far away as possible from trees, utility poles, and structures with loose components (fences or sheds).
- Secure any loose items around the car, such as bins and garden furniture, to prevent them from becoming damaging projectiles.