But the Mag Mile was teeming with pedestrians Wednesday night as warmer weather and cabin fever brought people out of their homes.
"While it is acceptable to leave your homes to go on walks near your homes and to purchase food and other essentials, you have to stay at home as much as possible," Lightfoot said.
Lightfoot said she would use every tool at her disposal to force compliance, including shutting down the parks and the entire lakefront.
By 6 p.m., much of Chicago's lakefront trail was cleared by police, making good on the mayor's threat.
She said she saw packs of people congregating as she drove up and down the lakefront on this milder Wednesday.
"Way too many people gathering like it's just another day. This is not just another day, and no day will be just another day until we're on the other side of the virus, which is weeks away," Lightfoot said.
Chicago police officers also broke up gatherings, which officials said could result in a warning, or citation and fine of up to $500.
"We're going to give you an admonition and if you don't turn right away and head home, then you're going to get a citation," said Lightfoot. "And if worse, yeah, we will take you into custody."
Repeat violators could be arrested.
"Because if we do not do this, Chicago is at risk," said Interim CPD Superintendent Charlie Beck. "Your families are at risk. The seniors in this city are at risk."
While Chicago police work to enforce the "stay-at-home" order, more of its officers have contracted COVID-19. Three new cases have been diagnosed, bringing the total involving the department to nine.
Mayor Lori Lightfoot warned that Wednesday night's lakefront closure could become the norm.
"If people don't take this in a serious way in which they must, I'm not going to hesitate to pull every lever at my disposal to force compliance if necessary," she said.
Meanwhile, the United Center will be used as a logistics hub during the coronavirus pandemic.
The arena and surrounding campus will be a staging area for first responders, as a place to distribute food and collect medical supplies.