National home value appreciation continued to climb sharply in August, up 6.6 percent compared with the same month last year. This increase is the largest such gain since July 2006, when home values rose 7.9 percent year-over-year.

Prices were up 0.4 percent from July, raising Zillow’s Home Value Index to $162,100 for the month. August is the third consecutive month in which monthly home values rose more slowly than the month prior.

Of the 382 metro areas where Zillow tracks prices, 85 percent saw prices rise in August, with two-thirds of the largest 30 metros seeing double-digit annual gains. That group includes Boston, where prices were up 10.1 percent year-over-year, according to Zillow. The sharpest year-over-year increases were in Sacramento (34.1 percent), Las Vegas (30.6 percent) and Riverside, Calif. (29.7 percent). Zillow predicts that U.S. home values will rise another 5.2 percent over the coming year, to approximately $170,500.

"August marked the end of one of the hottest summer home shopping seasons in years, as home value appreciation rates continued their rocket ride upward – perhaps dangerously so in some metro areas," Zillow Chief Economist Stan Humphries said in a statement. "Double-digit appreciation rates do help to lift homeowners out of negative equity and to entice sellers into a low-inventory environment, but this rapid growth is not normal and cannot and should not be expected to last. We are already beginning to see moderation in the monthly pace of home value appreciation, which will be good for the market overall and in the long term."

The number of completed foreclosures in August fell to 5.17 homes foreclosed out of every 10,000 homes nationwide, down from 5.27 homes in July. Foreclosure resales represented 8.28 percent of homes sold in the U.S. in August, down 0.3 percentage points from July and 3.1 percentage points from August 2012.