During the landing flare to runway 31, the airplane was "pushed to the left" by a "sudden gust of wind". The airplane nosed over and came to rest inverted. Both wings, the vertical stabilizer, and the rudder were substantially damaged. The flight instructor stated that there were no mechanical anomalies with the airplane that would have precluded normal operation. The flight instructor and the student pilot both reported that the wind was 330 degrees at 14 knots, gusting to 21 knots. The official weather observation, recorded at 1553, reported the wind as 340 degrees at 14 knots. The observation, recorded at 1553, reported the wind as 010 degrees at 12 knots.