"The bank's estimate of growth in Canada in 2015 has been marked down considerably from its April projection," the bank said in a statement announcing the news Wednesday.
Bank of Canada governor Stephen Poloz will address a news conference later Wednesday. CBC will livestream his remarks.
The bank's new rate — also known as the "target for the overnight rate" — is a 25 basis-point reduction from its previous 0.75 per cent level.
Before the Bank of Canada cut the rate to 0.75 in January, it had been at one per cent since late 2010.
The loonie lost almost a cent to 77.57 cents US on Wednesday's news.