It wasn't claimed that you suggested it would cease but murders in Chicago in January 2013 are running at a significantly higer rate than for all of 2012.
Oh Puhleeze just because it's too cold for lazy ass union police officers to look in the weeds doesn't mean there were no murders.
It was colder in Chicago this past month than in NYC, especially during the aforementioned week that the NYC went quiet. See charts: http://www.accuweather.com/en/us/new-york-ny/10007/month/349727?monyr=1/01/2013 http://www.accuweather.com/en/us/chicago-il/60608/january-weather/348308