Home prices in the Seattle metro area dipped for the fourth month in a row in January, in line with a nationwide decrease, according to the S&P/Case-Shiller 20-city index released Tuesday.

The average price of existing single-family homes in King, Snohomish and Pierce counties dropped 0.8 percent from the previous month, after a 0.5 dip in December. By comparison, the 20-city index dropped 0.1 percent in January, as it did the previous two months.

Year over year, the 20-city index is up 13.2 percent, less than the increase in 2013, and the second straight month the annual gain has slowed.

“The housing recovery may have taken a breather due to the cold weather,” David Blitzer, chairman of the index committee at S&P Dow Jones Indices, said in a statement.

January’s home prices in the Seattle area rose 11.9 percent over the year, but that is down from the 12.4 percent increase seen in December.

Over the year, every metro area in the index saw price appreciation, led by Las Vegas, with a 24.9 percent gain. Las Vegas also led in monthly price increases, with a 1.1 percent increase, and its 22nd consecutive monthly gain.

Twelve cities reported declining prices from December to January, with Chicago and Seattle posting the largest dips. Home prices rose in seven metros.

“From the bottom in 2012, prices are up 23 percent and the housing market is showing signs of moving forward with more normal price increases,” Blitzer said.

The Case-Shiller index covers roughly half of U.S. homes. It measures prices compared with those in January 2000 and creates a three-month moving average. The January figures are the latest available.

U.S. home prices jumped over the past two years, but average home prices in the 20-city index are still down at summer 2004 levels, according to S&P.

Average prices in the Seattle market, after climbing to 192 on the index in 2007, then falling to 128 in February 2012, was at 158 in January after four small declines.

Many economists see the price moderation as a positive trend, leading to a more sustainable housing market.

“The housing market is doing quite well,” Stan Humphries, chief economist at Seattle-based Zillow, an online real-estate marketplace, said in a statement.

“We remain far from normal in terms of appreciation rates, negative equity rates and mortgage rates, but we’re getting there, and a slowdown in appreciation is welcome.”

Ellen Haberle, an economist with Seattle-based Redfin, an online real-estate brokerage,
predicted prices will soon start to increase again.

“Without a boost in new inventory in the coming months, we are likely to see home prices in Seattle tick up as more buyers enter the market and compete for the limited number of homes for sale,” she said in a statement.

Coral Garnick: 206-464-2422 or cgarnick@seattletimes.com. On Twitter @coralgarnick