If your lock is seizing during this time of year, the likely culprit is cold weather. When the temperatures drop below freezing, if there is some moisture accumulated either on the on the strike or within the lockset, the lock could freeze. The moisture could be from a recent snowstorm or from the past, such as summer humidity that never dried out.
The first step to release the lock is to spray the strike with automotive brake cleaner. Only a spray or two is needed. The brake cleaner will remove the moisture and dry the parts. Next, spray the lock with a light coating of silicone spray. This should prevent the moisture from accumulating in the strike.
To prevent future freezing or seizing issues for all your locksets, use powdered graphite, silicone powder or Houdini Spray to lubricate the cylinders on a regular bases. These products will drive out moisture all times of the year. This regular maintenance will prolong the life of the lockset and ensure entrance in or out of a building at all times. However, do not use WD40 or other liquids. These products can actually lead to more dirt collection within the lock’s cylinder.