The terminal velocity of the average-sized house cat is 60 miles per hour. This is assuming that the cat has all four limbs extended, increasing its drag relative to its weight.
During a free fall, an object accelerates until it reaches the point where drag, or air resistance, is equal to its weight. The point at which this happens is called the terminal velocity. From that point onward, acceleration is zero, and the object's velocity remains constant for the rest of the fall. Although 60 miles per hour is still quite swift, it is a low enough speed to allow a cat to survive a high fall. It takes a fall of five stories or more for a cat to reach terminal velocity.