[bomberjet]

It all has to do with topography. Winnipeg sits on a barren plain at the bottom of a valley. So it's get's a bit colder. I follow weather from the states and the National Weather Service does a good job at explaining these sorts of things. It's clearly visible on their maps that the Red River Valley is usually colder than the surrounding areas. And yes the moraines (giant mountains lol) change the weather. Did you know the moraines are the leftovers shoreline of Lake Agassiz and it's pretty dang cool.

Another area that's interesting is the Sandilands. Drive out there and it's a different climate once you get into the trees. Temps are generally warmer.