WASHINGTON — July is generally a slow month for residential real estate sales, but last month was particularly slow in Northern Virginia.

Long & Foster Real Estate says closed sales in Arlington County were down 13 percent from July 2015. But Northern Virginia’s most expensive county got a little more so last month, with the median price in Arlington up 1 percent from a year ago at $625,950.

“Home sales slowed in many areas, while median sale prices increased, including in much of the Northern Virginia region,” said Jeffrey Detwiler, Long & Foster’s chief operating officer. “As the summer comes to a close, we anticipate that the housing market will remain healthy heading into the autumn season.”

Sales in Loudoun County were down 11 percent from a year ago. Closed sales in Fairfax County, Northern Virginia’s largest county by population, were down 6 percent.

Both saw prices rise.

The median price in Fairfax County was $492,500, up 1 percent. It was $450,000 in Loudoun County, up 3 percent.

Alexandria City saw a 7 percent year-over-year gain in sales, and a 10 percent jump in the median selling price to $536,000.