I have a 2004 Ranger Edge Regular cab.
I have a leak coming in on the passanger side and seems to be coming from the botton along the railing or just above. IT ONLY LEAKS IN THE WINTER

Last spring I parked my Ranger under a water sprinkler for 3 hours and no leak and no leaks all summer.
Now just sitting in the driveway with light rain I get water on the passengers side on the rubber mat. I have looked and looked and at a loss. It is not any antifreeze coming from the heater.
Any ideas or suggestions.
Thank you.