Overview

• The astronomical start falls on 22 September 2025 at 20:19, when the Sun crosses the celestial equator.
• At the equinox, day and night are roughly equal because the Sun is positioned directly above the equator.
• From this point in the Northern Hemisphere, daylight steadily shortens until the winter solstice on 21 December.
• Meteorological autumn runs each year from 1 September to 30 November, a fixed three-month period used for climate records.
• The change of seasons is driven by Earth’s approximately 23.5-degree axial tilt, which alters the Sun’s height and day length over the year.