The 610-hour private pilot reported in a written statement that "seconds prior to landing on runway 18L a gust of wind felt like it was pushing the airplane from behind." The pilot went on to say that while landing on the 8,001-foot long by 150-foot wide asphalt runway, the airplane began to drift to the left with braking and full aileron deflection. The airplane departed the left side of the runway and the right wing collided with a runway distance remaining sign. The airplane then reentered the runway and taxied to the ramp. According to the pilot, while 5 nautical miles east of the field the Automated Surface Observing System (ASOS) reported winds from 260 degrees at 14 knots. At the time of the accident the weather observation facility located at the airport reported winds from 290 at 16 knots, gusting to 21 knots.