Wood will naturally expand and contract with the seasons
Currently it is freezing cold in Oklahoma. Right now the temperature is 0 and the wind chill is even worse. The humidity in my home is also very low which doesn't help the wood in my house. To show you how bad it is here is a picture of my bamboo floors we just laid over the fall and how the cold weather in Oklahoma has affected it.
We followed the instructions and made sure to leave an expansion gap around the entire floor which was covered by the base molding, but as you can see my floors have shrunk because of the cold weather and low humidity so much there is a gap between my floor and molding. It should go back to normal once it warms up and the humidity increases but it was still a shock to see how far my floors shrunk.
Most cabinet doors are made from 5 pieces of wood; the center panel, the rails, and the stiles. When humidity levels decrease like they do in the winter your doors will shrink a little. Most people don't notice this on wood doors but it can be more noticeable on painted doors.
Some people will caulk the seams on cabinet doors which is not recommended. When the wood decides to expand or contract it will either cause the caulk to separate and ruin the finish on your doors, or if the caulk holds tight it can cause permanent damage to the door by causing the wood to split or warp.
The best thing you can do for the wood in your home is to keep your in home humidity levels anywhere from 35%- 60%. You can purchase a humidifier to install on your furnace or an inexpensive alternative is purchasing an evaporative humidifier from your local home store or online and to maintain a consistent humidity level in your home. If you do see shrinkage on your cabinets then increase the humidity level in your home and they should go back to normal in a week or two.
