I live in Ottawa, and have for the last 15 years, since moving here from Montreal.
You'll be surprised by the temperatures. I have a friend who married a woman from Mexico City, and she's had some difficulties adapting. You get wild swings in temperature from season to season. I know she was expecting the cold winters, but wasn't expecting the summers to be *hotter* than Mexico City. I remember visiting her home in Mexico in September, and being surprised to see a woman walking past in a full length fur coat, while we were walking around in shorts and sandals. It's all what you're accustomed to.
One thing to keep in mind is that they're very big on taking the humidity level, and crediting that towards the overall temperature. They call it the "humidex".
Basically, during the summer, this city gets very hot and humid for stretches. You can get temperatures of up to 35 Celcius, and then with humidex, is "feels like" 43 Celcius. Really, it just means that it's plenty hot, and because it's so humid, it feels rather sticky and uncomfortable, and it can be a little hard to breath on some days (particularly if you have asthma). Most of the time, they're not that hot though. Temperatures in the 25-32 range are pretty regular during summer.
Average winter temperatures are usually in the -12 to -17 range.....though the final two weeks of January, and first two weeks of February can be quite cold. I believe we're one of the two coldest national capitals in the world. Doesn't mean it's like that every day....but for about that four week stretch I mentioned, I think the coldest temperature I remember is about -40 Celcius. It's enough to make your eyelashes freeze in a few minutes. As others have said, windchill makes the difference. We've also had several warm winters lately. Again, hit or miss. In the last five years, I've seen one of the warmest winters I can remember, and one of the coldest. I've seen one of the winters with the least snow (as in, we had almost no snow until the end of January), and then one where the snowbanks were over my head.
Scarfs can help deal with that. The other thing to do is get a neck warmer. I usually do that myself, instead of getting a scarf. It keeps chill air from coming in the neck of your jacket, and you can stretch it over your mouth and nose.
All that having been said, it often sounds worse than it is. Yes, it can be cold, but as long as you wear proper gear, you'll usually be fine.
It's plain stupidity to try to be one of the "cool guys" walking around in running shoes and no hat when it's cold like that.
For the winter, I definitely recommend getting a winter jacket, particularly if you depend on walking or a bus to get anywhere.
My current jacket is a Northface, and has lasted me 10 years, and is finally getting onto its last legs. You can probably get something nice and reliable wtith a wind resistant coating in the $150-300 range for a jacket. Pants can cost anywhere between $50-125. Usually mitts are better than gloves. With individual fingers, gloves don't tend to keep you as warm......but they *are* more convenient. Get a proper toque. And winter boots with thermalite or some kind of similar liner. Good brands are Columbia, Northface, Sorel etc. (there are others...those are just ones I've used). If you can't do that, at least go and get yourself a good pair of thermal ski socks (much cheaper than a new pair of boots).
I don't usually see the need for long johns....at least not around the city.
Also, you can somewhat circumvent spending a lot on a jacket, by making sure you have a nice thick sweater to wear when you go outside. If that's on under your jacket, it helps give you the layers you need to avoid the temperature.
Mostly, I find that as long as I'm dressed properly, the winter weather doesn't bother me that much. There are lots of activities to do in the winter. We have the longest outdoor skating rink in the world (I think it still ranks as such). There's a winter festival called Winterlude, lots of local ski hills as close as 20 minutes north of the city, and lots of other activities. They just opened up our first water park this summer, and there's a second one coming in another year or two. The restaurant scene has been dramatically changing in the last few years, with some really nice places opening up. Ottawa used to have kind of a bland series of bars etc. but they've really been changing things in the last few years.
Aside from ski hills and skating rinks, there are lots of other things in general close proximity. As others have said, there are a bunch of museums...our national art gallery, the recently refurbished natural science musuem, the museum of technology, war museum, museum of aviation, etc. There are great hiking parks near the city in Gatineau Park, zip lines, paint ball facilities, plenty of golf courses, a "big" lake with rentable canoes and paddle boats right in the middle of the city, etc.
There's a decent gaming community, and probably the best gaming store in the city is right downtown, within walking distance of the University of Ottawa, and is called "Fandom II". They have pretty much *everything*.
As to cost of living......the last time I was in an apartment was about 7 years ago. Back then, I think my rent was something like $700/month for a 350 square foot apartment (basically bedroom, bathroom, living room, and kitchen). That included heating, but not hydro. That was not a furnished apartment. I had to bring my own mattress, dressers, etc. It *did* include a fridge and stove.
High Speed Internet can be had for about $30/month. Bell phone service (basic package) runs as low as $25 I think....but that's with no voicemail or anything.
Cell phones are available in pre-paid plans, as well as in contracts. Keep in mind, cellphone contracts in Canada are longer than in other countries (from what I've heard). They usually want you to sign for 3 years. Depending on if you're on a regular phone or a smartphone, costs can range anywhere from $30-100/month.
Groceries depend on how much you eat. Talking with friends, some couples eat for about $250/month, and others spend $450/month. Those prices are for 2-3 people. Depends on how much manufactured food you eat. If you're working on campus, and can get a student card for a cafeteria, you'd probably do better.
Living on the Quebec side used to be a lot less expensive. But I'm not sure what it's like now. I think it's gotten pricier than it was 10 years ago. If you speak no French, it's hit or miss what kind of service you get. I do speak French, but many of my friends don't, and sometimes have problems. My wife and I were shopping in Gatineau (the city on the Quebec side of the river from Ottawa), a saleswoman came and asked her in French if she wanted help, and my wife responded that she doesn't speak French. Instead of going to get an associate who speaks English, she just shrugged and walked away. That doesn't mean people get that all the time....it's just sometimes you get attitude, and other times you don't.
In general, I'd like to think that the people here are pretty polite. Many are very nice. It's humorous at times to sit at a stop sign, and see a bunch of people waving to each other to go through first. The people used to be "colder", but I find the city is starting to become more hip than it used to be. More multicultural, more interesting things to do.....it's starting to come into its own, I guess you'd say.
The population itself is pretty tech-savvy. We probably have one of the highest levels of education in the country on average (in terms of university degree holders etc.), a high degree of technical literacy, and lots of technical jobs. One of the nice things with the Universities here is that often they have boards where you can arrange to hitch a ride with other students who happen to have transportation on weekends and such. So, if you want to experience Quebec City, Montreal, or Toronto, you can usually find *someone* who is going for a weekend or long weekend, and get a lift with them, in return for gas money, if you want to have a chance to experience some really vibrant cities. Personally, I'd say if you have a chance to see Montreal (2 hours by car), Quebec City (5 hours by car), or Toronto (4 hours by car) while you're here, I'd jump on it (particularly Quebec City, which is absolutely beautiful).
I hope you enjoy your time here!
Banshee