Summer is good but, depending where you are in the country it can get very hazy, allot worse than the UK, winter is really clear, can see for miles! But very cold and generally lots of white stuff.
I have been flying allot this month in Ontario and have had about 20 fantastic days with only around 4 not flyable.
You will have to fly and see once you get here and work it all out as you go, just like you would at home.
Good luck
YYZ