Concealed carry and the murder rate there are probably not connected. Most of the murders involve gang members taking out other gangs.
They can’t legally carry in the first place.
I think you hit on it, the cold weather kept people inside.
I don’t doubt that concealed carry will make a difference but it won’t happen overnight. Legal carry in Detroit is building and the murder rate is creeping down but its taking time.
Last year there were 10 defensive shooting in Detroit all year, there have been 15 already this year.