The weather has been hinting at it for weeks, but the spring equinox will finally arrive this week in the Chicago area.
The equinox marks the moment when the sun crosses the equator from the Southern Hemisphere to the Northern Hemisphere, making the days longer and continuing the march toward summer.
So when is the precise moment that spring officially begins, at least from an astronomical perspective?
When does spring officially start?
According to NASA, the precise moment of the spring equinox will occur at 4:01 a.m. Central Daylight Time on Thursday.
While the conventional wisdom is that the first day of spring marks 12 hours of daylight and 12 hours of nighttime, that isn’t precisely true. Since the Earth isn’t a perfect sphere, and since the Earth rotates at different speeds at different latitudes, the timing of sunrise and sunset doesn’t perfectly line up with that 12-and-12 split on the date of the equinox.
For the Chicago area, Monday marks the date when we go over 12 hours of daylight for the first time since Sept. 24, according to Time and Date. On the date of the equinox, the city will receive 12 hours and 10 minutes of daylight, and that daylight amount will continue increasing until the summer solstice in June.
When is the summer solstice?
According to NASA, the summer solstice, the longest day of the year in the Northern Hemisphere, will occur at 9:42 p.m. Central time on Friday, June 20.
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