Home prices rose an average 5% annually across the nation in 19 major markets in August, according to real estate broker Redfin. Seventeen of the markets studied featured higher prices than a year earlier.

The Seattle-based company's home price tracker shows that Phoenix had the highest gain at 31% year-over-year, while Chicago suffered the most, down 4% from August 2011.

Redfin found that home sales grew 1.4% in that period, but fell 2.5% from July, a typical decline for this time of year.

Redfin Chief Executive Glenn Kelman said potential sellers holding out for more price gains in 2013 before listing their home are keeping sales from rising more. And many of today’s move-up buyers just plan to rent out their old place, he added.

The top six fastest-selling markets — the percent of homes selling in two weeks or less — are all in California: San Jose (52.3%), San Francisco (45.6%), Ventura (43.5%), Inland Empire (42.8%), San Diego (41.2%), Los Angeles (39.8%)

The percentage of listings that sold within 14 days of their debut increased slightly in August to 27.6% from 26.7% in July, the company said.

"Redfin saw a monster surge in August closings," Kelman said. "While September now seems likely to be down nearly 20% from August's peak, we were surprised after Labor Day to see a relatively large number of new customers begin touring homes for the first time, which has given us reason to be optimistic about the rest of the fall and even the year ahead.”