Sept. 22 (UPI) -- The arrival of fall coincides with an unusual twice-yearly milestone in Chicago, the so-called "Chicagohenge" phenomenon where the sunset and sunrise line up with the city's grid.
The Adler Planetarium said Chicagohenge arrives twice a year, at the start of spring and the beginning of autumn.
The planetarium said the fall Chicagohenge began Friday, and Monday offers the final glimpses of the phenomenon until next spring.
East-facing onlookers saw the sun framed by Chicago's buildings in the morning, and a similar sight could be seen from the west at sundown -- but some viewers this year reported cloudy weather spoiling the views.
Monday night's sunset -- about 6:47 p.m. local time -- will close out this year's Chicagohenge.
