Knox County had the biggest increase in sales for the three-month period ending June 30, up 24.3 percent from the previous year to 138 sales, according to a Maine Listings report issued Wednesday.

Lincoln County had the biggest decline in sales, down 17.5 percent to 104 homes sold.

Waldo County experienced the biggest jump in median price during the three-month period, up 17.2 percent to $150,000.

Lincoln County had the biggest median price decline, down 16.5 percent to $167,000.

Aside from the usual economic differences, one reason sales are surging in some counties and not in others is the lingering effect of harsh winter weather in some areas, said Marie Flaherty, president of the Maine Association of Realtors and broker/owner of The Flaherty Group in Westbrook.

“Their markets were delayed by the snow,” she said.

Sales of existing single-family homes statewide increased 18.2 percent in June. The Maine Listings report mirrors a report released Tuesday by RE/MAX Integra New England, which reflected similar trends in volume of sales and pricing.

According to the Maine Listings report, 1,788 existing homes were sold statewide in June, compared with 1,513 homes a year earlier.

The statewide median sale price for homes sold in June increased by about 1.5 percent to $187,700. The median indicates that half of the homes were sold for more and half sold for less.

Comparing volume of sales and prices over the three months of April through June, the 2015 numbers show an increase of 8.49 percent in the volume of sales and a 5.14 percent increase in price over the same period in 2014.

In Cumberland and York counties, where nearly half of all home sales occurred during that period, it has been more difficult for buyers to find homes in the middle price range of $200,000 to $400,000, Flaherty said.

However, there is hope on the horizon in the form of new development in communities such as Westbrook and Scarborough, she said, adding that it still could be a long time before supply catches up with demand.

“We are finally seeing developers confident enough in the market to build homes in that range,” Flaherty said.

Also on Wednesday, the National Association of Realtors reported a nationwide home sales increase of 9.8 percent over June 2014.

The national median price rose 6.6 percent to $237,700, the Realtors association said. Regionally, the Northeast experienced a 12.5 percent uptick in sales, it said, while the regional median price increased 3.9 percent to $281,200.