To some extent, the suburban landscape will be different during the two hours and 48 minutes the moon blocks the sun during Monday's solar eclipse.
Will nocturnal animals make an afternoon appearance? Will drivers need headlights to see? Will light-sensitive streetlights illuminate?
Hard to know, since Chicago hadn't been incorporated in 1806 (and neither cars nor streetlights were invented), the last time a total solar eclipse was visible in the area. Chicago hasn't even been this close to the path of totality since 1925, and observers here will have to wait until 2099 for the opportunity to see a total eclipse without having to travel, according to the Adler Planetarium.
Suffice it to say that in the absence of cloud cover, you will notice something different Monday -- a murky, twilight quality, perhaps, that will emerge just before noon and peak about 1:18 p.m.
Because maximum coverage will be 87 percent, the effects won't be as dramatic here as where the eclipse will be total and daylight will disappear.
"During those few minutes around 1:18 p.m., the sky will be eerily dim," said Eric Priest, an instructor in meteorology and astronomy at the College of Lake County in Grayslake. All bets are off if clouds block the sun, he added.
"If you are only able to watch the partial eclipse, your experience will be quite different," according to NASA. "Unless the sun is at least 75 percent covered by the moon, you may not even notice much illumination change at all unless you are aware the eclipse is happening."
The landscape dims when the coverage reaches about 90 percent. At 95 percent, even those who don't know an eclipse is happening will notice a change.
"The details, of course, will change depending on how aware you are of the exact timing of the event, and even your emotional state and its impact on your sensory acuity," according to NASA.
Observers are curious to see what happens.
"Bats may come out. The nighttime critters may get more active. That's one of the things we'll be observing and measuring," said Eileen Davis, an environmental educator with the Lake County Forest Preserve District.
The district will host a viewing "party" at the Ryerson Conservation Area in Deerfield, with a focus on how the eclipse will affect natural areas. Observers will listen for the calls of crickets and katydids, and watch for day-active animals to see if they behave as they do when they settle in for the night, she said.
Temperature variations and other information will be uploaded and shared on inaturalist.org.
"It's almost like a citizen science project," Davis said.
Daylight won't significantly decrease until about 12:55 p.m. then quickly reach its minimum before brightening again.
Even with a clear sky, Priest doesn't think we will be enveloped in darkness.
"Not positive, but I doubt it will become dark enough to trigger the streetlights," he said.
Visit https://eclipsemega.movie/ to see a simulation of how the eclipse will appear in your town.
All involved emphasize onlookers should not yield to temptation to watch the eclipse without certified protective eyewear (regular sunglasses don't qualify) or risk eye damage.
"There is no safe amount of time to look at it," Priest said. "I'm concerned, honestly, there are people who won't follow the rules on this."
So is this a once-in-a-lifetime opportunity?
The next visible total solar eclipse in the U.S. will be April 8, 2024. It will track northeast from Texas to Maine and cross the path of Monday's eclipse near Carbondale.