Phillip Patnaude, 28, was last seen early Saturday heading towards Lake Michigan after a night out.
Emergency crews were expected to begin looking for him again at Belmont Harbor after daybreak.
Meanwhile, family members and friends are praying and hoping to find the man
So far, the search at Belmont Harbor has been a challenging one as divers deal with frigid temperatures and murky conditions.
"The divers told me they have about five feet visibility. So, they can see five feet in either direction, but there's a lot of silt. So, when they get to the bottom, it might be a little silty and be reduced to two or three feet," said Sgt. Ray Mazzola of the Chicago Police Marine Unit.
Patnaude was last seen early Saturday after getting out of a cab at Wellington. His family believes he then went to check out the lake instead of going into his apartment.
"He loves being outdoors and loves natures and appreciates the aesthetics of beauty. So, while he doesn't go to the lake all the time on the weekends, it's not outrageous," a relative said.
When Patnaude didn't return home, his family and friends organized a search for him. They alerted police after finding his jacket at the harbor.
Divers searched for several hours Sunday, but because of safety concerns, they stopped diving after nightfall. Overnight police continued to search the surface of the harbor and brought in a robot to help.
"Each guy has 20 minutes. We did three divers, starting at about 2:30, and then right now, we're using an ROV. It's a camera that we can drive along the bottom to look for the victim," said Mazzola.
Phillip Patnaude is an engineer. He is engaged to be married in the fall. His friends and family say he loves the lake and may have headed toward it after the bars to check out the water and take a walk.