Though it still may feel like summer in Chicago, fall will officially start this weekend.
"We're getting closer to 12 hours of daylight and nighttime," NBC 5 Meteorologist Kevin Jeanes said.
The fall equinox, which takes place Sunday morning, will be when the sun shines directly on the equator. At that time, roughly everywhere on Earth will get approximately 12 hours of day and night, Jeanes said.
But that won't be reflected in sunset and sunrise times until Wednesday.
"7:43 a.m. Sunday is when fall officially begins," Jeanes said, noting that sunrise time that day will be at 6:38 a.m., and sunset at 6:46 a.m. -- which isn't exactly 12 hours apart.
"The sun is a disc, which means sunrise time is measured at the highest point of the disc," Jeanes said, adding that the same is true for sunset. "It takes time for the whole disc of the sun to cross below the horizon."
According to Jeanes, Wednesday, Sept. 25 will see a sunrise time at 6:41 a.m., a sunset time of 6:41 p.m.
Local
A few weeks after that comes the time change, when Illinois will roll back its clocks for the season. Here's what to know.
When is the first day of fall?
Feeling out of the loop? We'll catch you up on the Chicago news you need to know. Sign up for the weekly Chicago Catch-Up newsletter.
Fall officially begins at 7:43 a.m. CT on Sept. 22, 2024.
According to the Farmer's Almanac, that's when the astronomical event that marks the start of autumn will take place. In the Northern Hemisphere, the autumnal equinox occurs in September; in the Southern Hemisphere, it occurs in March.
When does daylight saving time end?
Currently, Illinois and several states across the U.S. are in daylight saving time, which began in spring. But that will soon come to an end as clocks "fall back" this season, giving residents a coveted extra hour of sleep.
But when does that happen?
The federal government mandates clocks roll back on the first Sunday of November each year. In 2024, that falls on Nov. 3.
What is daylight saving time?
Daylight saving time is a changing of the clocks that typically begins in spring and ends in fall. Under the conditions of the Energy Policy Act of 2005, daylight saving time starts on the second Sunday in March and ends on the first Sunday in November. On those days, clocks either shift forward or backward one hour.
When not in daylight saving time, the time is known as standard time.
As it stands, Illinois shifts between the two. The "spring forward" is when the state enters daylight saving time, and the "fall back" marks a return to standard time.
According to the website Time and Date, standard time is the local time in a country or region when daylight saving time is not in use.
"More than 60% of the countries in the world use standard time all year," the site says. "The remaining countries use DST during the summer months, generally setting clocks forward one hour from standard time."
Which states don't observe daylight saving time?
The annual time change will occur in Illinois and nearly every U.S. state, except two:
Arizona (although some Native American tribes do observe DST in their territories) and Hawaii.
U.S. territories, including Puerto Rico, American Samoa, Guam and the U.S. Virgin Islands, also do not observe daylight saving time.
Which is better: daylight saving time or standard time?
Previously, proposed legislation pushed for permanent daylight saving time, but that legislation ultimately fell through.
Still, sleep experts have long questioned the health of daylight saving time.
The American Academy of Sleep Medicine has pushed for a switch to permanent standard time for several years.
“By causing the human body clock to be misaligned with the natural environment, daylight saving time increases risks to our physical health, mental well-being, and public safety,” Dr. M. Adeel Rishi, who is chair of the AASM Public Safety Committee and a pulmonary, sleep medicine, and critical care specialist at Indiana University Health in Indianapolis, said in a statement. “Permanent standard time is the optimal choice for health and safety.”
Experts cited a "growing body of evidence" in recent years.
“Permanent standard time helps synchronize the body clock with the rising and setting of the sun,” Dr. James A. Rowley, president of the AASM, said in a release. “This natural synchrony is optimal for healthy sleep, and sleep is essential for health, mood, performance, and safety.”
It also mirrors similar takes from other organizations, including the National Sleep Foundation, which said "seasonal time-changes are disruptive to sleep health and should be eliminated."
How early will sunsets get?
You may have noticed: the days are getting shorter, and the sun is setting earlier. Already, Chicago has seen its final 7 p.m. sunset of the year, which fell on Sept. 15.
By Sept. 30, the sun will set at 6:32 p.m.
In the lead-up to daylight saving time, sunsets will slowly inch earlier, with the sun eventually setting at 4:41 p.m. as DST wraps up.
By the end of November, the skies will see a sunset as early as 4:30 p.m.
What is the autumnal equinox?
Also known as the fall equinox or the September equinox, the autumnal equinox marks the halfway point between summer and winter -- also known as fall.
As the Earth travels around the sun, it does so at an angle.
For most of the year, the Earth’s axis is tilted either toward or away from the sun. That means the sun’s warmth and light fall unequally on the northern and southern halves of the planet.
When the Northern Hemisphere is tilted toward the sun, that's called the summer solstice. This marks the first day of summer in the North and the first day of winter in the South.
One hundred and eighty days later, when the Southern Hemisphere is tilted toward the sun, it is called the winter solstice. This marks the first day of winter in the North and the first day of summer in the South.
The halfway points between solstices are the autumnal and vernal equinoxes. The word equinox comes from two Latin words meaning equal and night. That’s because on the equinox, day and night last almost the same amount of time — though one may get a few extra minutes, depending on where you are on the planet. This provides approximately 12 hours of day, followed by 12 hours of night.
