Unfortunately I don't currently have a garage spot for my Mini and when I came home from a short vacation after some serious rain; I came home to a fair amount of water on my drivers seat. I do not have a sunroof. I will say one of my least favorite features of the car is if you roll down the windows and any amount of water has collected on the roof it all comes pouring into the car. I did not leave the window down but maybe somehow it didn't auto roll up the last 1cm after auto rolling down 1cm and it was cracked open? Anyone else have an issue with inclement weather and a wet interior?

 

With another brand of car water in the cabin could get in via blocked body water drains which allowed the catch basin to overflow and this would have water in the cabin, on the floor.

Another source of water in the cabin could come from the door. The membrane that separated the wet side of the door from the dry side would fail -- mainly due to age/exposure -- and water in the dry side would leak into the cabin. Wet carpet trim along the door bottom was a sign of this.

Water on the seat suggests a leak up high. With no sun roof that leaves the door or side window weather stripping/seals suspect.

With one of my previous cars whenever I washed the car I noticed a few drops of water running down the inside of the driver side window. I just avoided directing a lot of water at that area. I checked and no water came in through that leak when driving in the rain or when the car was parked in the rain, so I never bothered to try to fix the leak.

Dry the seat. Might have to open the door and aim a fan to blow air in the cabin. Be sure there is no water on the cabin floor. Don't know about MINI but at least one brand of car I'm familiar with has a very expensive security module located on the cabin floor under the driver seat. Any water in the cabin ends up there and the water will ruin the module in no time.

Then make sure the door is closed and the window is up all the way. Have a helper dump buckets of water on the car and you inside check for any signs of water. Obviously there should be none.

Also, do not limit your leak suspicions to the door or side glass. Be sure to check the rear and front glass doesn't leak.

 

I had small amount of water collect inside the door panel, which is apparently normal. Noticed it when changing out door speakers.

Whenever I drive I always hit the switch on the window and note that the window moves ever so slightly up as if it hadn't fully moved when the door is closed. You might want to read here and see if it would help https://www.newtis.info/tisv2/a/en/f...lator/1LKsK9oT