How can I prevent a wooden door from expanding and binding when it rains?
I am going to guess that you have a wood door causing the problem. If you have checked the original installation and frame alignment and feel that cannot be changed, then the only real solution is to plane it down so it closes properly when damp or humid. You can install extra or new weatherstripping to assure it has a good airtight seal,especially in dryer times when it may shrink a bit.