I would agree, and also suggest flushing the system with fresh fluid. In addition to the sticky caliper, which may be causing the warm weather problems, you may have moisture in the system, which is known to cause brake problems in freezing weather. As a matter of fact moisture in the system can be a cause of corrosion, which can cause warm weather problems.
In short, moisture in the system could be the root cause of both the cold and warm weather problems. Note that now that the caliper has been affected, you’ll need to change it.