The U.S. welcomes autumn with the 2025 equinox.

Photo of Marco Carrillo in Unsplash

Today, at 2:19 p.m. EDT, the autumnal equinox, also known as the northern equinox, officially marks the beginning of astronomical autumn in the Northern Hemisphere.

What does this moment mean?

The equinox is the moment when the sun's rays shine directly onto the Earth's equator. This causes the length of day and night to be almost equal around the world.

Although the term “equinox” evokes that exact balance, in practice the day typically has a few extra minutes of daylight due to how the Earth’s atmosphere refracts sunlight.

Changes that autumn brings

The days will begin to progressively get shorter, which will be especially noticeable in the northernmost areas.

Temperatures tend to drop, and seasonal phenomena intensify: leaf color changes, cooler nights, cleaner air, and more variable weather conditions.

Fun facts

This equinox also marks the end of astronomical summer.

In many regions of the US, although astronomical autumn begins today, its effects (such as cooling weather or leaf fall) are felt a few days later. Climate, latitude, and local natural factors greatly influence how quickly the change is experienced.


In Boston, the beginning of autumn is celebrated in a very special way: parks like Boston Common and the Public Garden begin to turn shades of red, orange, and gold, attracting locals and tourists alike.

The air is getting crisper, marking the transition to longer nights and perfect days for strolling along the Charles River or visiting fall markets. This change of season also heralds long-awaited New England traditions, such as leaf-peeping excursions to see the foliage in all its splendor.

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Sources:

• Space
• The Washington Post