Fall blooming is triggered by strange weather patterns. It is more prevalent in certain varieties and in fact is exploited in bloom-a-thon and encore azaleas. The fall blooms are using up what would normally be next spring's flowers.

Some causes of fall blooming include a dry summer and moist fall and/or warmer climates including a warm fall. For some reason, fall blooming is more common in Georgia according to Dr. Sandra McDonald. Plants which are not sufficiently hardened off or are exposed to unseasonable warm spells can start bloom prematurely. These blooms are seldom satisfactory and many times get frozen before opening fully. In any case, the seasonal bloom is lost. Avoid application of nitrogen after late spring, but phosphorus and potassium may be applied during the growing season. Application of nitrogen too late in the season can hinder hardening off in the fall and cause this problem.

Basically, sometimes it happens....not anything to really worry about unless the plant goes whole hog and starts a tremendous flush of new growth (that would likely be killed by weather).