Why humid air changes the fit
The Building America Solution Center’s guide to water-damaged building materials explains that wood products swell when they take on moisture and shrink when they dry out, leaving gaps, and that uneven wetting and drying can make wood warp. The same page notes that the moisture content of wood follows the relative humidity of the surrounding air: wood kept at 50% relative humidity or below settles at about 9% moisture content, while at 75% it rises to about 14%. That is why a door that closes easily in dry weather can have less clearance in a humid spell.
Track when and where it rubs
Before anyone planes or trims the door, keep a short log: the date, where it catches (a top corner, the latch side or the bottom), and whether the latch still engages. The EPA’s Care for Your Air guide suggests a moisture or humidity gauge, available at most hardware stores, to check indoor humidity. Writing down the reading each time turns “it felt damp” into a record you can show someone. Photos of the gap taken from the same spot help too; our guide to photos for a repair estimate covers what to capture.
Lower indoor humidity where you can
The EPA recommends keeping indoor humidity between 30 and 50 percent, and says to open windows to lower humidity only when it is not humid outdoors. Its guidance on controlling moisture at home lists bathroom and kitchen exhaust fans that vent outside, a clothes dryer vented outdoors, and dehumidifiers and air conditioners to take moisture out of the air. Drier air will not necessarily restore the fit, especially if the wood has warped. If a bathroom stays steamy, see why a bathroom fan can run without clearing condensation; for a damp basement, compare what a dehumidifier does and what a sump pump does.
Rain and leaks are a different problem
If the door sticks mainly after rain, or you see staining, soft wood or peeling finish near the frame or sill, liquid water may be getting in rather than humid air alone. The Solution Center’s pan flashing page notes that doors interrupt a wall’s water protection layer and that the sill is the location most vulnerable to water intrusion. Its guide to air sealing exterior doors calls for inspecting doors for signs of water damage or dry rot and repairing that damage. Have a qualified professional find where the water comes from before the door itself is adjusted.
Check the fit before removing wood
Trimming a door while it is swollen can leave too large a gap once the wood dries and shrinks. Rubbing is also not always swelling: the fit depends on how the door and frame were set and on any weatherstripping. The air-sealing guide notes that installers plumb and square a door when setting it, that weatherstripping should press tightly without making the door difficult to shut, and that a finished door should open freely with no drag on the threshold. Ask whoever looks at it to check alignment, hardware and weatherstripping, and to explain what evidence supports the fix they recommend.
If an exit door will not open normally, have it looked at promptly instead of waiting for drier weather. More general repair questions are on our home construction and general repairs page.