The Chart above shows the temperatures from Midnight through 2pm this afternoon. It shows that temperatures have really nosedived across the state (except the extreme east and southeast). Temperature drops have been rapid, with 20-30° drops in 2-3 hours. Ottumwa (OTT on the chart) dropped 23° in only 1 hour. The temperature difference from the coldest reading to the warmest in the state (Given by COLD and WARM on chart) shows a 62° difference. This is a season changer, with readings falling from the 50s and 60s to the single digits and teens by tomorrow morning.

FYI Chart Codes are
SUX Sioux City
DSM Des Moines
MCW Mason City
CID Cedar Rapids
BUR Burlington
DBQ Dubuque
OTT Ottumwa
ALO Waterloo