When there’s a high moisture content in the air, wood absorbs some of it—causing it to
expand, swell, or shift within the door frame.
Other common causes include:
Poor ventilationindoors Inadequate door sealing or weatherstripping Warped frames or thresholds Old or improperly installed hinges Shifting foundationsin Texas clay soil
...
yes or no to each question:

• Does your door only stick during the summer or on rainy days?
  ...
  If you answered “yes” to 3 or more, it’s time to take action—either through repair or a humidity-resistant replacement.
  ...
  Quick Fixes for Sticking Doors
  If you’re not ready to replace the door just yet, try these easy fixes:
  1.
  Identify the Problem Spot
  Close the door and look for rub marks.
  Chalk or lipstick along the edges can help you find where it’s catching.
  2.
  Tighten or Adjust Hinges
  Loose hinges can throw off alignment.
  Tighten screws and check for warped hinge plates.
  3.
  Sand the Edge
  Slightly sand the sticking area.
  Be careful not to remove too much—you may need more next season.
  4.
  Repaint or Seal
  Apply a weather-resistant sealant or paint to all six sides (including the top and bottom) of a wooden door to reduce moisture absorption.
  5.
  Use a Dehumidifier
  Especially in older homes with poor ventilation, a dehumidifier can help regulate indoor moisture.
  If these fixes don’t solve the issue—or if you notice structural problems—it may be time to replace the door altogether.