The Canadian Real Estate Association says the recent rise in mortgage rates caused people who already had mortgage approvals from their lenders to move their decisions forward.
Mortgage rates rose 0.2 percentage points the week of August 22, but many prospective buyers locked in rates with their banks, and the impact of higher rates is not expected to be felt until later in the fall.
The August numbers also seem high by comparison with a year ago because sales activity had dropped sharply last summer after Ottawa tightened mortgage rules.
That tightening dampened enthusiasm to buy homes last fall, but by the spring, Canadians were again shopping for housing.
Sales rose sharply in most major cities and especially Vancouver Island, Victoria, Greater Vancouver, the Fraser Valley, Calgary, Edmonton and Greater Toronto.
The average price of a home was up 8.1 per cent at $378,369, with price rises in Toronto and Vancouver driving most of the increase. The average price of a Vancouver house was $775,811 and in Toronto, it was $523,228.
Average prices dropped in the Fraser Valley, Ottawa-Gatineau and Kitchener-Waterloo, Ont.
CREA doesn't expect the strong numbers will last this fall.
"That pool of homebuyers [who had locked in mortgage rates] has largely evaporated, so demand may soften over the fourth quarter," said CREA chief economist Gregory Klump.
The big year-over-year gains will persist because sales were so weak in fall of 2012, he said.
Around 325,180 homes traded hands across the country so far this year. That is 2.9 per cent below levels recorded last year and overall sales are expected to stay below 2012 levels.