New York, NY —

There is some sun in the weekend weather forecast which means that a rare occurrence in the Manhattan skyline should be visible. At sunset tomorrow, the sun will set in exact alignment with Manhattan's street grid, turning the city's canyons into a kind of modern-day Stonehenge.

Every single cross-street in Manhattan, from 14th street up, will be illuminated for the last fifteen minutes of daylight. It's one of only two days a year when this happens, though the effect will be visible for a day or two before and after.

It happens because the length of Manhattan is tiny compared with the distance between the earth and the sun so the sun's rays are essentially parallel when the hit -- and fill all of the island's cross streets simultaneously.

Sunset on Saturday will be at exactly 8:18pm. After that, the point of sunset migrates slowly north, bringing us longer days. The effect will return again on July 11th.