Well, I did some checking, and apparently my memory is not as good as I thought it was. Or maybe people always seem to exaggerate when they look back on bygone times, especially the bygone times of one's youth. Anyway, on this date, January 6, there has been only one other time since 1948 that the temperature has gotten below zero in Joplin, when it got to -1 in 1968. In Springfield, there have been only two times since 1888: 1968 when it got to -1 and 1912 when it got all the way down to -12.
If we broaden the scope of our search a little, however, and include the whole month of January instead of one particular date, the results tend to do a little more toward confirming my recollection of very cold temperatures. For instance, there was one nine-year period between 1977 and 1985 that was particularly cold. During six of those nine years, the temperature dipped down to -11 or below at least once during the month of January, reaching a nadir of -13 two different years. In fact, the three consecutive winters starting with the winter of 1976-1977 were so frigid that some meteorologists suggested that we were entering a mini ice age.
The coldest temperature on record in Missouri happened on February 13, 1905, when a reading of -40 degrees was recorded at Warsaw. The -4 that we are experiencing today doesn't seem so bad compared to -40. Warsaw is also tied with Union, by the way, for the hottest temperature ever recorded in the state. Both towns registered 118 degrees on July 14, 1954.