ideas for garage door drainage issue

You might have to adjust the door to put 3/4” blocks underneath it, but this is a much better solution than cutting the weatherstripping to permanently let critters in. The “best” solution is to cut in a trench drain inside the door and pipe it outside to a French drain or pop up emitter. The “best” solution may not be a practical one. I would probably just open the door occasionally to let water out.