What causes damp passenger floor board on 2000 Lincoln ls?

I would check around windshield for leaks,door frames and the weatherstripping,feel up under dash to see where it`s wet or if wet at all,if not feel how wet it is closer to door,most likely weather stripping and such.Hope it helps. I had the tube for the sun room come disconnected from mine, and everything kept getting wet. What you do is take the o-darn handle off, pull the front pillar cover off, usually a snap fit component, and the seat belt cover (snap fit as well) be careful not to be to agressive. After you pull the roofliner down only on the side you are working on. You should see a small 1/8" tube that is disconnected from a drain barb. hook it up and enjoy a water free environment. Special note. on mine it just seems the hose shrank over time. It may happen again, but at least I put it back on there. It was a bummer in a down pour I could see water coming in the car driving down the road and the front piller was wet.