I totally believe that this is true on average. But there are a few weeks in the January/February when we're sitting under a high pressure system with clear skies, no wind, and -30C temperatures. Power generation needs to be able to handle annual extremes, not just averages.
According to https://www150.statcan.gc.ca/t1/tbl1/en/tv.action?pid=251000... January and February are among the most productive wind energy months in Canada, with the summer months being notably lower. I couldn't easily find stats about nr of low-wind days. I guess Canada also has the advantage that it's a big country so local weather variations doesn't necessarily matter as much.
