The pilot reported that a gust of wind caused the tailwheel-equipped airplane to swerve left during landing roll. He was unable to regain directional control of the airplane before it departed off the left runway edge, striking a concrete pad and runway edge light which caused the airplane to nose over. The airplane’s fuselage, vertical stabilizer, and rudder were substantially damaged during the accident. The pilot reported that there were no preaccident mechanical failures or malfunctions with the airplane that would have precluded normal operation. The pilot reported that the surface wind was calm when he listened to the airport’s automated weather broadcast about 11 minutes before landing. A weather report issued about 5 minutes after the accident included a 4-knot surface wind from the northeast. Based on available weather information, a variable wind direction likely prevailed at the time of the accident that resulted in an unexpected left quartering tailwind during the landing.