But the warmup was expected to take a jarring jump in the coming hours and days — sending the battered region into a temperature roller coaster. The thaw gave cities and towns a chance to begin assessing deaths, injuries and damage to infrastructure that the deep freeze had caused. But the fast-rising temperatures were also causing a new set of risks to contend with, including the potential for flooding, abundant potholes and clogged stormwater drainage systems.
In Wilmington, Illinois, the Police Department warned of flash flooding as ice moved downstream. And at Oakland University in Detroit, a library was closed Friday because of a water main break that flooded the building.
The difference in temperature that the Chicago region could experience by Monday: 73 degrees, from Thursday morning, when the city saw a low of 21 degrees below zero, to Monday, when it may be 52.
“It’s fairly rare to see this much of a turnaround in temperature in this short of time,” said Todd Kluber, a meteorologist with the National Weather Service.
Chicagoans will go from a deep freeze Wednesday and Thursday to a mild warmup Friday, as air from the Pacific begins to move into the region. Then there is more weather whiplash: on Saturday, fog and freezing drizzle. On Sunday, more drizzle. On Monday, rain.
In Illinois river cities, officials eyed the warmer forecast nervously. Deputy Chief Don J. Gasparini Jr. of the Winnebago County Sheriff’s Office said he had been monitoring the Rock River in northern Illinois for the possibility of ice jams and floods.
Gasparini said the rain predicted by meteorologists would also be unwelcome, with the ground frozen and snow piles abundant. “The rain is not going to have any place to go,” he said.
The cold spell caused significant destruction. The deaths of at least 25 people were being linked to the weather system. Among the deceased: A 72-year-old woman found unresponsive in her garage Friday morning in Germantown Hills, Illinois.
This article originally appeared in The New York Times.