TORONTO (Reuters) - The impact of the fast rise of the Canadian dollar versus the greenback is set to hit home in October as third-quarter corporate results start rolling across Bay Street.

Since the beginning of the year, the Canadian dollar has surged more than 18 percent against the US dollar, and is up around eight percent in the third quarter alone.

The currency's rise has been on the back of a weak greenback, a sizzling domestic economy, robust commodities prices, and narrowing North American interest rate spreads.

While the currency is giving consumers a bigger bang for their buck, some sectors of corporate Canada are having a difficult time adapting.

"(The higher Canadian dollar) will slow down the rate of growth of earnings and obviously it's not going to be evenly distributed across the sectors," said Ian Nakamoto, director of research at MacDougall, MacDougall & MacTier.

The higher Canadian dollar makes manufacturers less competitive in foreign markets at a time when the weaker greenback will give a boost to US competitors.

Plane and train maker Bombardier Inc, Canada's biggest manufacturer, is an example. It engages in currency hedging to limit the impact of foreign exchange moves, but that won't alleviate all the damage of a higher Canadian dollar.

A research note by Desjardins Securities said it expects currency to cut Bombardier's third-quarter earnings per share by one US cent.

Desjardins also says every one Canadian cent move in the Canadian dollar cuts net income at flight-simulator maker CAE Inc by C$500,000.

But Nakamoto said he sees a silver lining for Canadian manufacturers. He points out that in the 1990s, the greenback was strong and the Canadian dollar was weak, giving US manufacturers a drubbing and forcing them to restructure.

"Now I would say they are probably one of the most competitive in the world and the currency is in their favour and their ability to sell overseas is improving because their price is right and secondly, their margins are definitely improving because they took the painful restructuring during the 1990s."