These are daily coldest high temperatures for the past 100 years. January 6 was tied for eighth lowest high, with a high of 2°F (which, by the way, came before 1 a.m.). The lowest high temperature St. Louis has recorded is -5°F, on Christmas Eve, 1983.
These are daily coldest low temperatures for the past 100 years, plus January 6. Monday's low of 8°F didn't come close to cracking the top ten. January 18, 1930 holds the record for the past century, with a low of -19°F.
Our average temperature January 6 was -3°F. That ties for 14th among lowest average temperatures in the past 100 years. Three times in the past century (all in the 1980s), the average was -8.5°F.