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Monday, October 18, 2021

The first day of fall 2021 – when summer ends [Termin]

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Autumn is approaching inexorably. We will welcome a new season of the year next week. When will the calendar autumn start and when will the astronomical autumn start? Check the exact dates.

We associate autumn with the fact that the days are shorter and the nights are getting longer. This is because the sun goes down earlier and earlier and rises later and later.

Seasons. Where do they come from

What are the seasons of the year on Earth? Not from the changes in the distance of our planet from the Sun, which varies slightly, but from the combination of two factors: the tilt of the Earth’s rotation axis relative to the plane of its orbit and the orbital motion around the Sun. Therefore, the lighting conditions change in different times of the year in a given hemisphere.

Autumn equinox 2021. Astronomical autumn. Date

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When is the first day of astronomical autumn this year? The period from the autumn equinox to the winter solstice is considered to be astronomical autumn in our hemisphere. The autumn equinox occurs when the sun passes through the point of Libra. The Earth then crosses the point on its orbit where the sun’s rays fall perpendicular to the equator and are simultaneously tangent to its surface at the poles.

The time of the fall equinox usually falls on September 22 or 23. In 2021 it will be exactly Wednesday on September 22 at 21:21.

Calendar autumn 2021. Date

The beginning of calendar seasons always falls on one specific day. The first day of calendar fall in autumn 2021 falls on September 23. It will last until December 21 – then the calendar winter will begin.

Weather autumn 2021

In addition to the calendar and astronomical autumn, we also know the concept of meteorological autumn. The weather autumn always falls on the same period. It starts on September 1 and ends on November 30. This concept was introduced by meteorologists and climatologists. It is used to always refer to the same period when comparing statistical or climatic data, because astronomical and thermal seasons have “moving” dates.

IMGW weather for October

Autumn bird migrationMaria Samczuk / Adam Ziemienowicz / PAP

Main photo source: Shutterstock

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