The average date of the first subzero low in Ottumwa? Hillaker put it at around Dec. 7, making this year a rare case of a weather-related event arriving right on time. But even there, recent years have run a bit late. It has been eight years since subzero weather arrived earlier in December.
Still, this year is nothing compared to the coldest years. December 2000 was far colder. With 16 days when temperatures hit zero or below, all of which came from Dec. 11 or later, the month holds the modern record for the most in December.