The southeastern U.S. has plunged into record-low temperatures, affecting 18 million people under a freeze warning across Alabama, Florida, and Georgia. The cold spell moved from the Northern Plains and brought an abrupt transition to wintry temperatures.

Some daily records were shattered, including a low of 28 degrees in Jacksonville, Florida. In Florida, temperatures led to a "falling iguana advisory" as iguanas froze into survival mode and fell from trees.

Meanwhile, parts of the Great Lakes and Northeast experienced significant snowfall, causing hazardous driving conditions. Forecasters expect temperatures to rise by the end of the week.

The cold air over the Great Lakes’ relatively warmer waters created ripe conditions for significant snowfall in some communities along the Great Lakes and downwind, farther inland in Pennsylvania and New York.

The lake-effect snow was expected to add inches Tuesday, and forecasters said a new storm system would bring additional snowfall Wednesday.

Communities downwind of Lake Erie and Lake Ontario also woke up under a winter weather advisory Tuesday, with the National Weather Service predicting anywhere from 2 to 6 inches (5 to 15 centimeters) of snow in some New York cities, including Niagara Falls, Rochester, Buffalo, Syracuse and Jamestown.

For many, they are the first few inches of snow in a season that typically delivers around 100 inches (2.5 meters) or more by spring.