I don't think it gets really hot, the only time I went to Canada was in the summer about 5 years ago.. It was raining for about 5 days... sucks. I think you can say it was about spring's temperature.
Canada is bigger than the USA and has just as much variation. Temperature charts for major Canadian cities are at this link: http://www40.statcan.ca/l01/cst01/phys08b.htm
Haha, into the low 40's (celcius). With humidity, into the 50's. And the winter, oh man. Coldest I ever walked in was -57 with windchill at 6 in the morning.