A persons tent damaged my car at a car show and he says that he isn't liable for the damage because it was an act of god(storm).

If his negligence damaged your property, he would be liable for the damages which you incurred, assuming you didn't have any agreement in connection with the car show which limited your right to pursue such claims, or limited your recovery.  However, I can't tell from your question whether the other party was negligent.  If an unexpected tornado picks up my car parked in my driveway and crashes it onto your car parked in front of your house, I may not be liable, because I haven't acted negligently.  If, however, I see the tornado coming and have time to park in my garage and don't do so, then a jury may say that I have behaved unreasonably under the circumstances (negligently) and could hold me liable for the damages you suffer.  You say that the other party's negligence caused the damage to your car - in what way was the other party negligent?