When Does Fall Start In 2024? 5 Things To Know

F​all officially begins this weekend, even though teases of the cooler temperatures the season brings have already swept into parts of the U.S. this month.

H​ere are five things to know about the fall, or autumnal, equinox:

1. Fall's start time on Sunday, Sept. 22, will depend on where you live: I​f you are in the Eastern time zone, then fall officially begins at 8:43 a.m., local time. The start of fall will be at 7:43 a.m. in the Central time zone, 6:43 a.m. in the Mountain time zone and 5:43 a.m. in the Pacific time zone.

(​MORE: Fall Foliage Tracker)

2​. Here's why there's a down-to-the-minute time that marks fall's beginning: Twice a year, around March 20 or 21 and Sept. 22 or 23, the sun's rays shine directly over the equator. In the Northern Hemisphere, these are known as the spring, or vernal, equinox and the fall, or autumnal, equinox.

The specific time, in the case of this year 8:43 a.m. EDT, marks the passage of direct sunlight over the equator from the Northern Hemisphere to the Southern Hemisphere.

Because of that, day and night are balanced to nearly 12 hours each all over the world. You can see this in the half sunlit and half nighttime (dark areas) satellite image from the Sept. 23, 2019 equinox.

From this point on, daylight in the Northern Hemisphere will gradually grow shorter until the winter solstice, which occurs on Dec. 21, 2024. That's because the Earth will be in the process of tilting away from the sun in the Northern Hemisphere.

4​. Everything is opposite for the Southern Hemisphere: South of the equator, the September equinox marks the beginning of spring.

Daylight will now grow longer until December's start of summer in places like Australia and South America, since that part of Earth will receive the sun's most direct rays.

5​. Fall and autumn are used interchangeably, but there's a difference in what they mean. Find out more with our full explainer here.

Chris Dolce has been a senior meteorologist with weather.com for more than 10 years after beginning his career with The Weather Channel in the early 2000s.