PORTLAND, Ore. ( TheStreet) -- The leaves are dying and crisp breezes are blowing in, but real estate listings are getting some new life as the fall selling season heats up.Existing home sales are up more than 17% since last year, while the price of those homes has risen 13.5% over the same span, according to the National Association of Realtors. Meanwhile, the backlog of homes on the market has dwindled 5% from a more than six-month supply of 2.4 million in July 2012 to a 5.1-month supply of 2.28 million this summer. As a result, the percentage of "distressed" and foreclosed homes on the market dropped from 24% last year to 15% in July. "Mortgage interest rates are at the highest level in two years, pushing some buyers off the sidelines," says Lawrence Yun, NAR chief economist. "The initial rise in interest rates provided strong incentive for closing deals. However, further rate increases will diminish the pool of eligible buyers." Z) reporting that 23.8% of mortgages are still underwater despite rising prices -- down from 31% last year, but still including nearly 60% of mortgages that exceed the value of their home by 20% or more -- there are still plenty of people looking for a way out. With help from the National Association of Realtors and Zillow, here are some hints for buying a home in the fall without getting left out in the cold by winter: 1. Treat it like a sale: If it works for cars and outdoor appliances this time of year, why not houses? According to National Association of Realtors numbers, there's a natural discount of about $7,000 after Labor Day. It's a bit less in the West or in the South, where the "cold" months only increase demand, but Midwest home prices fall by an average of $10,000 between August and September while Northeast prices drop nearly $20,000 by October.