After a frigid Saturday and a sunnier, milder finish to the weekend, the seasons will officially change in Chicago by Monday afternoon, as the vernal equinox occurs.
Although meteorological seasons are typically defined as periods of three months beginning at the start of every third month, astronomical season are aligned with biannual equinoxes and solstices.
The vernal and autumnal equinoxes mark the beginning of spring and fall, while the winter and summer solstices define the astronomical start of those seasons respectively.
This year's vernal equinox will occur on Monday, March 20 at 4:24 p.m., which will mark the astronomical beginning of spring.
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On the first day of spring, also the day of the vernal equinox, daytime and nighttime hours are roughly equal, just as they are during the autumnal equinox in late September, according to the Adler Planetarium.
From the vernal equinox up until the summer solstice, daylight hours will increase as dark-sky hours decrease. The date of the summer solstice marks the day of the calendar year with the highest amount of daylight hours.
Although temperatures aren't quite spring-like on Sunday, with sunny skies and highs in the low 40s, it will likely feel a bit more like spring later this week.
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Skies are expected to be mostly cloudy on Monday, with highs reaching near 50 degrees. From there, rainfall is likely in the middle of the week with highs approaching the mid 50s.
