Astronomical versus meteorological seasons: What’s the difference?
OMAHA, Neb. (WOWT) - September 1st marked the first day of Meteorological Fall in the northern hemisphere. September 22nd marks the first day of Astronomical Fall in the northern hemisphere.
You may hear your local meteorologists mention meteorological and astronomical seasons throughout the year. Yes, there is a difference.
Astronomical seasons are caused by the tilt of the Earth on its axis as it rotates around the sun; these are the seasons you may see on a calendar.
Equinoxes occur when the sun passes directly over the equator – marking the start of the astronomical spring and fall seasons. Day and night are roughly the same length (12 hours) around the equinox.
The start of astronomical fall this year – the autumnal equinox – lands on September 22nd.
Solstices occur when the sun’s apparent path is the farthest north or south of the equator. Solstices mark the start of the astronomical winter and summer seasons – or the “shortest” and “longest” days of the year.
Meteorological seasons are used primarily for the documentation of climate information. Each season is a nice, even 3-month period, falling more in line with our civil calendar.
While the start of astronomical seasons will change a few days from year to year, meteorological seasons will always start on the first days of December, March, June, and September - respectively.
Less variation in season start dates and season duration allow us to more easily compare climate statistics from year to year.
More information on astronomical and meteorological seasons can be found here.
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