Chicago Police officers ride their bicycle as they are patrolling on the sidewalk during a cold day in Chicago, Tuesday. (AP Photo/Nam Y. Huh)

The first major cold spell of the season plunged parts of the southeastern U.S. into record-low temperatures Tuesday, delivering a shock for 18 million people under a freeze warning across Alabama, Florida and Georgia. Meanwhile, several inches of snow blanketed areas along the eastern Great Lakes as the blast of cold air moved through.

The direct shot of Arctic air affecting the eastern two-thirds of the country migrated east — and far southeast — from the Northern Plains, which was hit with gusty chills and snow over the weekend. For much of the Southeast on Tuesday, that meant an abrupt transition into wintry temperatures after reaching well into the 70s and 80s (21 to 27 Celsius) in recent days.

Some daily records were “absolutely shattered,” said meteorologist Scott Kleebauer, including a low of 28 degrees Fahrenheit (-2 Celsius) at the airport in Jacksonville, Florida, on Tuesday morning. That broke the previous record low of 35 degrees set in 1977.

The southeastern U.S. will face a few more colder-than-normal days before warming up later in the week.

Iguanas begin to “freeze” and fall from trees when temperatures dip to 40 degrees (4 Celsius) or below, according to Kleebauer, a forecaster with the National Weather Service’s Weather Prediction Center. Those temperatures were widespread upstate in Florida on Tuesday.

“Iguanas, because of their reptilian nature, they go into this kind of survival mode, and their system basically shuts down,” he said. “They’re not used to those types of temperatures. They only see those only a handful of times a year, if that.”

Posts of the stunned reptiles trickled in on social media as Floridians also faced unfamiliar weather.

“A lot of times you kind of sneak into fall and then you eventually get winter,” Kleebauer said. “This was more — it was warm there for a long time and then all of a sudden it’s a shock to the system with how cold the shot was.”

Visitors to Orlando’s theme parks might have thought they were back in the northern destinations they had left behind for a warm vacation, forcing them to bundle up as low temperatures neared freezing. As far south as Fort Lauderdale and Miami, early-morning temperatures dipped into the upper 40s. Even in the sunshine, the temperature wasn’t expected to reach 70 degrees (21 Celsius) on Tuesday.

Agriculture officials in Florida said they hadn’t heard of any problems due to the cold front, but they were holding their breaths until Wednesday morning following one more cold night.

Across West Virginia, a predawn coating of snow and ice contributed to dozens of accidents Tuesday before the sun came out and road conditions improved.

More than 14 inches of snow on Monday and Tuesday enabled the White Grass Ski Touring Center in the northern mountain’s Canaan Valley to open for cross-country skiing.

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.

Barbara Butch is the village clerk and librarian for the town of Ubly in the center of eastern Michigan’s thumb region. The village was socked with snow Monday, getting nearly 8 inches by Tuesday morning, according to the National Weather Service.

“It just kept coming down,” Butch said.

On the West Coast, an atmospheric river taking aim at California was expected to bring heavy rains and mountain snow later this week.