The astronomical autumn officially commenced on September 22, 2025, at 20:19 Central European Time, marking the annual equinox when day and night reach nearly equal length across the globe. This celestial event occurs when the sun appears directly above Earth's equator, creating what astronomers call the "equal night" phenomenon. The equinox signals the beginning of cooler seasons in the Northern Hemisphere while bringing spring to southern latitudes.

According to astronomical explanations, the equinox results from Earth's axial tilt and orbital path around the sun. During this biannual event, the sun's rays fall exactly above the equator, causing sunrise and sunset to occur at precisely 90 and 270 degrees respectively. While meteorologists consider autumn to span the months of September through November for statistical purposes, the astronomical autumn begins specifically at the moment of the September equinox.

In Germany, the seasonal transition brought noticeably cooler temperatures and divided weather patterns across the country. The German Weather Service reported maximum temperatures reaching only 18 degrees Celsius, with some regions experiencing persistent rain while others maintained drier conditions. Northern areas saw clearer skies, while southern Germany required rain gear as temperatures in mountainous regions hovered around 10 degrees.

Following the equinox, daylight hours will progressively shorten in the Northern Hemisphere, with locations like Spain losing nearly three minutes of sunlight daily. The sun will rise approximately one minute later and set one minute earlier each day, accelerating the transition toward winter conditions. Meanwhile, the Southern Hemisphere begins its opposite seasonal journey toward spring, demonstrating the global balance created by Earth's orbital mechanics.