My wooden door scrapes the frame when it's humid. Why does it do that and what can I do?

Your wooden door is absorbing moisture from the air, causing it to swell and rub against the frame. This happens most often on the latch side or bottom edge. First, tighten all hinge screws; a loose hinge can cause sag and bind. If that doesn't fix it, the door itself has swollen. You can carefully plane or sand a small amount off the sticking edge. Guessing wrong and removing too much wood will leave you with a drafty door in dry weather. If the problem persists or involves a warped frame, have a carpenter assess it.