Weather right now is -15 degrees Celsius in Ottawa (1 pm). That's probably a tic below average for this time of year, but not much.
This site is definitely worth checking out - you can see a million things in Ottawa so it really depends on what you're interested in. The Royal Canadian Mint is very interesting, if you're interested in art the National Gallery of Canada has a fantastic collection. Parliament Hill is great as well, although I'm not sure how interesting that would be to non-Canadians. If you have anywhere in particular in mind and I've been there I could tell you what I thought. Hope this helps.