Astronomical date of the beginning of autumn and the reason for the delay in the equalization of night and day in Jordan

2025-09-22 2025-09-22T09:27:13Z

Arab Weather - Dr. Ammar Al-Sakaji, head of the Jordanian Astronomical Society, said that the autumnal equinox will occur on Monday, September 22, 2025, at 9:19 p.m. Jordan time, officially marking the end of summer and the beginning of autumn, astronomically speaking.

Arab countries on the first days of autumn, astronomically, autumn rains include 8 Arab countries.

Autumnal equinox in the northern hemisphere and vernal equinox in the southern hemisphere

It is known that the moment of the autumnal equinox in the northern hemisphere corresponds to the moment of the vernal equinox in the southern hemisphere at the same time, as the two equinoxes occur at the same moment globally, with time differences depending on the geographical location .

The sun is perpendicular to the equator and the night and day are equal

At this moment, the sun's rays are perpendicular to the equator, so the solar radiation is distributed equally over the two hemispheres of the Earth. The Earth's axis of rotation is perpendicular to the sun-Earth line, neither tilting towards the sun nor away from it. At that moment, the length of the shadow on the equator is at its minimum. The sun rises from the geographic east and sets from the geographic west, and the hours of day and night are approximately equal, without taking into account the effect of the atmosphere .

The reason for the delay in the equal length of night and day in Jordan in 2025

However, atmospheric physics – including refraction, scattering, polarization, reflection, and absorption – delays the actual day of equal night and day. The difference has been calculated for Jordan's location at approximately four days. Therefore, Friday, September 26, 2025, will be the day when the hours of day and night are equal in the capital, Amman, and its suburbs .

Astronomically, autumn continues until the winter solstice, which will occur on Sunday, December 21, 2025, at 6:03 PM Jordan time. Thus, autumn lasts approximately 89 days, 20 hours, and 43 minutes .