The high end of the US real estate residential market shows few signs of losing steam.

The number of US residences sold for $1.0 million or higher in August this year rose by 6 per cent from a year earlier, while luxury home sales hit double-digit gains in 20 major cities, figures showed.

The data comes from the realtor.com® Luxury Home Index, looking at the top 5 per cent of all residential sales in 90 US counties.

The combined median age of inventory in the 90 luxury markets surveyed was 121 days, down by nine days or 6.9 per cent year-over-year. Additionally, two thirds of luxury markets are seeing inventory move faster than this time last year. In 50 of the 90 counties analyzed, the luxury tier has an entry point of at least $1 million, while 70 markets continue to see yearly price growth.

The figures suggest that the US residential market has considerable contrasts, the compilers of the data said.

"The conditions in the luxury segment are quite different from the market overall – it's really a tale of two markets," Danielle Hale, chief economist for realtor.com®, said. "Although US median listing prices show signs of slowing growth, luxury prices are moving in the opposite direction in many places. For the second consecutive month, we've seen more markets with double-digit, entry-level luxury price growth than in the past four years."

Since March, Sarasota, Florida, has remained the nation's fastest-growing luxury market, with sales prices up by 21 per cent since last June. Half of all luxury homes in Sarasota sold within 165 days, 22 per cent faster than the previous year. Queens, New York; Santa Clara, California; Boulder, Colorado; and Collier, Florida, rounded out the top five counties, each seeing yearly price growth of between 13 and 15 per cent.

After declining for 24 months in a row, Miami luxury prices finally saw growth this January, and have now reached the highest price gains since July 2015. Miami's luxury market is currently growing at 2.2 per cent year-over-year.

Most California luxury markets show no sign of a slowdown. Some seven counties are in the top 20 fastest growing markets, all of which saw double-digit growth in June. San Francisco, Sonoma, and Santa Clara -- up by 10, 13, and 15 per cent, respectively -- are showing that there is still room for growth. On the other hand, San Mateo, Sacramento, San Luis Obispo, and Santa Cruz are holding steady.