Hot, humid outside weather conditions tend to drive moisture into cooler and dryer areas like an air conditioned home. However, that is just one of many possible sources of high humidity. Other common major factors are an oversized air conditioner that short cycles, moisture migration from wet foundations or crawl spaces, and indoor sources of moisture that are not adequately exhausted to the outdoors. Make sure indoor exhaust fans from your bathrooms, kitchen, and clothes dryer are working properly and venting to the outdoors, rain drains away from the house, and if you have ductwork in the attic or crawlspace, make sure it is sealed airtight.
