The fall equinox arrives Tuesday, marking the moment when the sun crosses the celestial equator, moving southward, and day and night are approximately equal in length everywhere on Earth. After the equinox, days grow shorter in the Northern Hemisphere and longer in the Southern. It is the official start of autumn.

CHICAGOHENGE  

Chicago’s urban grid — most of which runs at a roughly 26-degree angle to true north rather than aligned with cardinal directions — produces a specific optical phenomenon twice per year: around the spring and fall equinoxes, the setting sun aligns with certain east-west Chicago streets, producing a corridor of light visible down the length of the street and generating striking photographs. The phenomenon is nicknamed ‘Chicagohenge’ by analogy to Stonehenge’s solstice alignment.

The sun sets on Tuesday and lines up perfectly with certain Chicago streets because Chicago’s grid is tilted. It happens twice a year, at the equinoxes. It is beautiful, and it requires no further context. In a week that included five networks walking out, a fiber cable grounding 1,000 flights, and an AI that almost started a war with China, the sun still sets at exactly the right angle to turn Wabash Avenue into a corridor of light.

WHAT HAPPENS NEXT  

▸  The sun sets Tuesday aligned with Chicago’s east-west streets

▸  Autumn begins

CONFIDENCE: HIGH

Fall equinox Tuesday Chicagohenge Chicago grid setting sun east-west street alignment from NPR confirmed reporting.

SOURCES

▸  NPR — fall equinox Chicagohenge September 22, 2026