WASHINGTON — U.S. home prices posted a robust gain in August — another sign that the American housing market remains strong despite economic fallout from the coronavirus pandemic.

The S&P CoreLogic Case-Shiller 20-city home price index, released today, showed that home prices climbed 5.2% in August from a year earlier, accelerating from a 4.1% gain in July. The gain was stronger than economists had expected.

Phoenix (up 9.9% from August 2019), Seattle (up 8.5%) and San Diego (7.6%) posted the biggest gains. All 19 cities in the index recorded price increases. The 20-city index excluded prices from the Detroit metropolitan area index because of delays related to pandemic at the recording office in Wayne County, which includes Detroit.

Helped by rock-bottom mortgage rates, the U.S. housing market has been a source of strength as the U.S. economy climbs back from an April-June freefall caused by the pandemic and the measures taken to contain it.

The National Association of Realtors reported last week that sales of existing homes shot up 9.4% in September and that the median selling price of a home climbed 15% from a year earlier to $311,800. And the Commerce Department reported that home building rose 1.9% in September on a surge in construction of single-family homes.