When is the best time to replace cracked or damaged bricks?

The best time of year to tackle a brick replacement job is in moderate weather.  In a perfect world, it would be a little cool, no wind, a constant temperature of 55 degrees, and fully overcast skies.  In the real world the brick mason must adapt procedures to accommodate the prevailing weather conditions.  In the late fall we might use accelerators or even baffle a job and supply heat, for example.