In meteorology, autumn begins on September 1st. However, the September equinox marks the beginning of astronomical autumn in the Northern Hemisphere and spring in the Southern Hemisphere.
Autumn in 2025 in the Northern Hemisphere will begin on September 22nd at 6:19 PM UTC (8:19 PM Spanish Peninsular Time), according to calculations by the National Astronomical Observatory. This season will last approximately 89 days and 21 hours, and will end on December 21st with the beginning of winter.
The beginning of autumn in the Northern Hemisphere is defined by the instant the Earth passes through the point in its orbit from which the center of the Sun crosses the celestial equator in its apparent southward motion. On the day this happens, the length of day and night practically coincide. This event is also called the autumnal equinox.
When autumn begins in the Northern Hemisphere, spring begins in the Southern Hemisphere.
Some of the phenomena of astronomical interest during the fall of 2025 will be the Draconid meteor showers, whose peak is expected around October 8, the Orionids, with their peak around October 21, the Leonids, with their peak around November 17, and the Geminids, with their peak around December 14. The full moons of autumn will occur on October 7, November 5, and December 5.
ALWAYS BETWEEN SEPTEMBER 21 AND 24
The beginning of autumn can occur on at most four different dates on the calendar (from September 21 to 24). Throughout the 21st century, autumn will begin on September 22 and 23 (the official Spanish date), with the earliest onset occurring in 2096 and the latest in 2003. Variations from one year to the next are due to the way the calendar’s sequence of years (some leap years, others not) fits with the length of each Earth’s orbit around the Sun.
The beginning of autumn is the time of year when daylight hours shorten most rapidly. At Iberian latitudes, the sun rises more than a minute later in the morning than the previous day, and sets more than a minute earlier in the afternoon. As a result, at the beginning of autumn, the time the sun is above the horizon decreases by almost three minutes each day.
