I have a 2010 Ford Mustang and every time it rains it sounds like the water is accumulating in the door?

I have a 2010 Ford Mustang and every time it rains it sounds like the water is accumulating in the door. Is there a drain or plug that I need to attend to?

Yes there are drains in the bottom of the door. One near the front and one near the rear…

Look at the bottom of the door. You should see a couple of small holes that are intentionally left open to drain water. If they are plugged with dirt or debris, they could allow water to build up inside the door and that water will eventually cause the bottom of the doors to rust through. I suggest using a bit of stiff wire to poke up inside those holes to clear the blockage and allow the water to drain out. You may have to do this several times.