Fall officially arrives with the autumnal equinox

Fall has officially arrived. Summer has come to an end, meaning cooler and shorter days are on the horizon. 

The change in seasons occurs with the solstice or the equinox determined by the Earth’s tilt and orbit around the sun. 

What is the equinox?

The Earth is tilted at a 23.5-degree angle, and as it travels around the sun, the Earth’s axis is tilted toward or away from the sun.

During the equinox, the Earth’s axis and its orbit line up, allowing the sun’s rays to shine directly on the equator. This means that both hemispheres get an equal amount of sunlight.

Meteorological Fall vs. Astronomical Fall

The meteorological seasons are calendar-based, whereas the astronomical seasons rely on the Earh’s position to the sun. 

Meteorological fall occurs from Sept. 1 to Nov. 30. The meteorological seasons are broken down evenly into 3-month periods based on temperature and weather cycles. 

Astronomical fall typically starts between Sept. 21 and Sept. 23. This varies because of leap years, which can shift the start date by a day or two. 

Why do we lose so much daylight?

We have been slowly losing more and more daylight since the summer solstice in June, and will continue to lose more daylight until the winter solstice in December. The largest daily loss of daylight occurs in September, especially as the autumnal equinox approaches.

The Earth’s 23.5-degree tilt is the main reason we see daylight changes throughout the year. Your latitude also plays a role as well.

This time of year, the Northern Hemisphere tilts away from the sun, leading to a decrease in daylight. Areas located closer to the equator will see less variation in daylight hours as opposed to areas located closer to the North Pole.

Our team of meteorologists dives deep into the science of weather and breaks down timely weather data and information. To view more weather and climate stories, check out our weather blogs section.