The chance of a tornado hitting either of those airports over a 3 week period in June is extremely slim. The chance of significant thunderstorms with straight line winds and hail hitting them is considerably higher. A parking garage would provide more protection from those than your driveway as the roof would block hail and there is no chance of toppled trees etc. causing damage.

I would think that human-caused damage is more likely in a public garage than your own driveway. Over that 3 week period countless other vehicles could perform parking maneuvers near your vehicle which could pose an accident risk and thus a risk of damage to your vehicle.