Boston’s robust downtown condominium market is getting hotter, with sales up more than 25 percent in the third quarter and the median selling price near a peak level, according to figures scheduled to be released Thursday.

The report by LINK, a Boston data-tracking company, says condo sales in 12 core areas of the city totaled 1,043 between July and September, a 26.3 percent increase compared with the same period last year.