In a written statement, the pilot said he departed in his glider with an observed thunderstorm approximately 50 miles from the airport. About 2 hours later, after hearing that other glider pilots had returned to the airport due to the approaching storm, he returned as well. During the approach to the airport, it was raining and the wind was gusting to 38 knots. The airplane landed with a left crosswind. During the landing roll, the left wing impacted the ground and the glider ground looped. The glider sustained substantial damage to the empennage. The pilot reported no mechanical deficiencies and stated the accident could have been prevented if he had landed sooner.