On May 16, 2006, at 1815 central daylight time, a Cessna 525, N545TG, registered to Interstate Warehousing Inc., operating as a 14 CFR Part 91 business flight, collapsed a left main landing gear on landing roll out at Murfreesboro Municipal Airport, Murphreesboro, Tennessee. Visual meteorological conditions prevailed and an instrument flight plan was filed. The airplane received substantial damage. The airline transport pilot and 6 passengers reported no injuries. The flight originated from Newport News, Virginia, on May 16, 2006, at 1715 eastern daylight time. The pilot stated upon arrival in the Murphreesboro area he was cleared by Nashville Approach Control for a visual approach to runway 18 at Murphreesboro Municipal Airport. The pilot tuned up the Airport Terminal Information System information on the airplane radio. The winds were reported at 240-degrees at 3 knots and the runway was wet. The pilot entered the traffic pattern, completed the before landing checklist, lowered the landing gear, and approach flaps on base leg. The pilot turned the airplane on final approach, lowered the flaps to the full down position, and activated the anti skid. The pilot landed the airplane on the first one third of the runway. The pilot stated a front was approaching the airport and upon touchdown the wind had changed and heavy rains had started. The airplane started hydroplaning at midfield and there was insufficient runway remaining for the pilot to initiate a go-around. The airplane went off the runway sideways, collapsed the left main landing gear, and came to a complete stop. The pilot completed the engine shutdown and he and the 6 passengers exited the airplane. After exiting the airplane the pilot stated he observed the left flap had separated from the airframe and there was structural damage to the left wing. The pilot stated to the NTSB investigator-in-charge that he lost directional control of the airplane as it was hydroplaning down the runway. He further stated there was no mechanical problems with the airplane before the accident.