Infrastructure is definitely required - safe bikelanes are almost a "must have". I live on the highest point in copenhagen and bike to the lowest. Granted it's not a mountain. Weatherwise, and I bike to work every day - 6-7 km btw, the summer is great, fall is lots of rainy days (but having quality rain clothes helps). In the winter, which granted is mild - but goes down to maybe -10c, you can still bike, even in heavy snow and when the bikelanes haven't been cleared.

I love biking - taking the car would be horrible, especially parking wise, and the public transportation, while good and regular is just not for me.