The pilot received a weather briefing before taking off on an aerial traffic patrol for a local radio station. He was issued a special VFR clearance to follow a pre-established route. However, after departing, he encountered thunderstorm activity. He returned to the departure airport and hovered until the thunderstorm activity subsided. After about 30 minutes, the pilot departed again, but was unable to conduct the flight as planned. With the weather deteriorating, he received clearance to another airport. When he was about one mile from the airport, the visibility was reported as 1/2 mile. He reported that when he was about 100 ft AGL, he turned northeast into the wind to get close to the boundary road and fence and to get visual references. Also, he stated that the visibility through the bubble was distorted by the heavy downpour and bubble fog. While attempting a hover landing, he touched down, tail low, moving rearward. The rear part of the skids and the tail rotor hit the ground and control was lost.