Existing home sales stumbled in August for the fourth time in five months as strained supply levels continue to subdue overall activity, according to the National Association of Realtors (NAR). Sales gains in the Northeast and Midwest were outpaced by declines in the South and West.

Total existing home sales, which are completed transactions that include single-family homes, townhomes, condominiums and co-ops, retreated 1.7 percent to a seasonally adjusted annual rate of 5.35 million in August from 5.44 million in July. Last month’s sales pace is 0.2 percent above last August, and is the lowest since then.

Lawrence Yun, NAR chief economist, says the slump in existing sales stretched into August despite what remains a solid level of demand for buying a home. “Steady employment gains, slowly rising incomes and lower mortgage rates generated sustained buyer interest all summer long, but unfortunately, not more home sales,” he said. “What’s ailing the housing market and continues to weigh on overall sales is the inadequate levels of available inventory and the upward pressure it’s putting on prices in several parts of the country. Sales have been unable to break out because there are simply not enough homes for sale.”

The median existing home price for all housing types in August was $253,500, up 5.6 percent from August 2016 ($240,000). August’s price increase marks the 66th straight month of year-over-year gains.

“Some of the South region’s decline in closings can be attributed to the devastation Hurricane Harvey caused to the greater Houston area,” Yun said in a statement. “Sales will be impacted the rest of the year in Houston, as well as in the most severely affected areas in Florida from Hurricane Irma. However, nearly all of the lost activity will likely show up in 2018.”