Ready your cameras - one of Chicago's most photogenic moments is almost here.
Chicagohenge comes only twice a year, bringing crowds of people into the streets to see the sun framed by city's skyline.
What is it?
The phenomenon occurs during the fall and spring equinoxes. The grid system the city is based on allows for spectacularly composed views of the rising and setting sun.
"Chicago’s streets are laid out on an east-west direction so at this time of year, around the equinox, that’s when the sun rises almost perfectly in the east and sets in the west and that’s when the sun setting will just line up with the street alignment," Mark Hammergren, a lead astronomer for the Adler Planetarium, told NBC 5.
The name is a nod to the iconic and prehistoric Stonehenge in England.
When is it?
Hammergren said those hoping to bear witness are best served looking east shortly before sunrise and west before sunset in the day's leading up to and after this year's autumnal equinox, which falls on Monday.
He said viewers can start looking Thursday and might see it as late as Sept. 27.
"Starting now, the sun will be higher when it crosses the east-west path, but as the days go on you’ll see it getting lower and lower," Hammergren said.
Currently, sunrise happens around 6:30 a.m. and the sun sets just before 7 p.m.
Though the weekend will see some rain and clouds, you might still be able to witness the stunning sight. NBC 5 Storm meteorologists say Saturday morning might bring clear skies, but Sunday likely won't be the best day for viewing. On Monday, conditions will likely be better in the evening hours. Check the forecast each day for the most updated information.
The highly-anticipated solar occurrence will return in the spring if you miss it this year.
Where can you see it?
Experts recommend standing on unobstructed east-west streets in the city and using skyscrapers to frame your view for the best pics.
"The skyscrapers are perfect for that," Hammergren said. "If you’re out on Congress and you see the sun setting and lighting up all the buildings. It's really about where people can set up their cameras."
Michelle Nichols with the Adler Planetarium told the Chicago Sun-Times her favorite spot is at the western end of the 606 Trail.
Gorgeous photos have been taken along Washington Street in the city's Loop and along Randolph Street. If you take some cool pics, send them to firstname.lastname@example.org!
Is it only in Chicago?
The extraordinary sight isn't just unique to Chicago. Acclaimed scientist Neil deGrasse Tyson wrote about Manhattanhenge for the American Museum of Natural History.
"For these two days, as the sun sets on the grid, half the disk sits above and half below the horizon," he wrote. "My personal preference for photographs. But the day after also offers Manhattanhenge moments, but at sunset, you instead will find the entire ball of the sun on the horizon."
Hammergren noted, however, that New York'd grid isn't as perfectly east-west as Chicago's is.
"They're tilted a little bit so that's why their dates are off from us," he said.