The warning comes as a recent COVID surge has moved Chicago and many surrounding counties into the CDC's high community transmission level. However, returning to a mask mandate seems a long way off.
Heading into the Memorial Day weekend, with many people planning to gather with family and friends, Chicago Commissioner of Public Health Dr. Allison Arwady urged people to wear masks when indoors with the city in the high risk category.
"We ask everybody for this short time period while we are in high put that mask on especially if you are in an indoor crowded setting," Dr. Arwady said.
But, will people voluntarily comply? Psychiatric experts say compliance rates definitely increase if people are required to do something, but after two years, mandates are tough as people suffer from COVID fatigue.
"You can only demand conformity or mandate conformity for a period of time until people become weary of it," said Dr. Robert Shulman at Rush University.
WATCH | Dr. Arwady on what it means when Chicago moves to 'high' COVID risk
Chicago's not alone. In the Chicago area, Cook, DuPage, Lake (IL), McHenry, Will and Grundy counties all appeared as "high risk" on the CDC's map when it was updated Thursday afternoon.
Despite the recommendation to wear masks, it is not a requirement for now.
"I'm going to wear my mask inside, it's probably the right thing to do," Michael Pattis said.
What does is mean to be at high COVID level?
"It's hard to breathe, plus it should be your choice to wear one or not," Raymond Rodgers said. "I'm not going to do it."
In Chicago, compared to the start of the pandemic when 50 to 60 people a day were dying, the current average is less than one per day.
Despite an increase in hospitalization numbers, they're still a fraction of what they were during the omicron peak a few months ago.
At Edward-Elmhurst Health, COVID-related hospitalizations have more than doubled in the past five weeks.
But compared to other surges, fewer patients are critically ill.
"Because of vaccinations and the protection they have and because of anti-viral treatments, we're not seeing severe illness lead to death or ICU care as much," Dr. Jonathan Pinsky, Medical Director of Infection Control at Edward Elmhurst Health, said.
But health officials are keeping a close eye on how stressed the healthcare system may become.
"If we see an increase in stress, than we'll have to take other measures," said Dr. Rachel Rubin, at Cook County Dept. of Public Health.
Rubin said hospitalizations can remain low if people do the right thing and mask up.
"What I would hope is for the management of these public spaces - whether it's a retail establishment or event space - that they would do their best to ask people put masks on," Rubin added.
To keep it under control, Arwady said more Chicagoans need to get boosted. The rate has remained low for months, with only 42% of eligible residents having received a booster shot.
In addition, Arwady said residents should avoid crowded indoor gatherings, limit gatherings to small numbers and test right away if you have symptoms.
Anyone who tests positive is asked to isolate for five days and if they are feeling better, they can go in public while wearing a mask for the next five days.