When I took the door panel apart, I noticed some dirt buildup near some of the drain holes; might have been a contributing factor. They are all clear now.

 

I have read from other Monte Owners that the window glass seal on the door deteriorates and may cause the water to infiltrate the cabin and doors. This usually occurs on cars that are outdoors in the sun all the time. Check this link for other ideas.

https://montecarloforum.com/forum/fw...lem-fix-26663/

 

Be aware it could be the drains for your fresh air intake are clogged with leaves underneath the windshield grate.

This happened to my dad's Buick. The windshield bottom has a rubber or foam strip that is suppose to keep larger items from passing under i.e. leaves, needles, etc.
But over the years the rubber or foam degrades AND windshield replacement techs often do Not replace what is needed or rip it out or don't place the windshield edge under the locating fingers for the plastic grate system.

If large items get past, they can clog the drainage system that is not designed for large items, just water.
Then the water can over flow down the fresh air intake, into the car.

Take care