Expert: Kenneth Saunders - 1/8/2009

Question
Is it truth or myth that a wall clock should not be hung on an outside wall due to inconsistencies of temperature and humidity as compared to an interior wall?

Answer
myth today but perhaps truth in days of old in drafty, un-heated, un-insulated, un-air conditioned farmhouses? Anyone today that concerned with the timekeeping accuracy of their clock, perhaps should rely on their microwave for the time instead?

You specifically made references to "inconsistancies" in your question, no mention of rusting or warping or deterioration concerns.
I took your concern to be thus in the area where time keeping "inconsistancies" might be your concern. The myth I have heard for years never says WHY one should never hang a clock on an outside wall. Your microwave with its' quartz movement will keep better time than any interior wall hung clock. Best wishes