Since 2014, when this blog started, I’ve run a couple of articles about when the average date of the coldest day of the year is for everywhere in the United States. Here is an update that now includes an interactive map to show you when you can expect the coldest day of the year to occur where you live. For me in Athens GA, the magic date is January 16. Your results may vary. Of course, in any given year, the weather will affect when the coldest air reaches your location, but on average you can expect the temperature to start increasing after this date as we head towards spring. Visit the interactive map here.
Just for fun, why do you think the coldest day of the year is not the day with the least amount of sunlight? The answer is basically for the same reason that the daily temperature is not usually at noon when the sun is highest. You can read an explanation here.