I maintain that the correlation between those two factors is not nearly as strong as people make it out to be when trying to explain away the violence that American sunbelt cities impose on their residents. -20 vs 80 is an extreme example (Minneapolis probably has as many of those days as Memphis has days above 100, which surely has its own negative impacts on the appeal of active transportation), but yes I suspect that you could find more people walking about in below freezing temperatures in a city that is built with pedestrians and their safety in mind than you will find out and about in balmy temperature in a city that is built to put the car above all other forms of transportation. I don't even think it's particularly counterintuitive if you think about it for a bit. Think about a snowy Christmas market, and then think about a 4' wide, unevenly paved sidewalk flanked by a steep ditch on the side of a 6 lane highway in the most beautiful weather you can imagine. Which of those scenes would you be more surprised to see someone walking through?