Here is a website that has monthly temperature and precipitation maps for the continental US going back to the 1920s. You can use it to look up what the anomalies and extreme climate were for any month since then. Just for fun I produced the map below showing the extent of extremely cold temperatures that occurred in January 1977 when I was in college in Michigan. I did not realize the expanse of cold conditions covered most of the US! You can try it out at https://usafacts.org/issues/climate.
