The pilot of the tailwheel-equipped airplane reported that, during the landing flare, he felt a wind shift push the airplane left of centerline. He applied opposite rudder, but the airplane touched down "skewed" to the right. The airplane then exited the runway to the right and ground looped on an adjacent field. The airplane sustained substantial damage to the left wing. 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 wind was variable at 6 knots at the accident site. He added that, during the short final leg of the approach, the wind was from about 210º and that, during the landing flare, the wind shifted to from about 280º. The airport's automated weather observation station reported that, about 20 minutes before the accident, the wind was from 310º at 9 knots and that, about 30 minutes after the accident, the wind was from 180° at 8 knots. The pilot landed the airplane on runway 20.