The period from late summer to early fall is the time of year that the U.S. begins to gradually sink into the meteorological sweet spot for sleeping temperatures (as long as you’re not stuck in one of the seemingly endless heat waves plaguing the South).

The general rule of thumb is to keep your thermostat set somewhere between 60 and 65 degrees, or maybe a little higher if you have a fan that can add a little “wind chill” while you sleep.

But you don’t have to worry about the electric bill from cranking your air conditioning when the temperatures outside are already in the peak coziness-factor range (a technical term, I assure you).

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(SEPTEMBER OUTLOOK: Strengthening El Niño rewriting your first month of fall)

By September, more and more major population centers start to see their average nighttime low temperatures falling into the upper 50s and low-to-mid 60s, including New York (62.3 degrees), Atlanta (65.9 degrees), Los Angeles (64.2 degrees), Chicago (57.1 degrees) and Washington. (57.9 degrees).

Keep in mind, however, that these are only averages. Those sizzling Southern heat waves as summer gives way to fall mean that millions of people are left dreaming (or, I guess, not dreaming, given the whole harder-to-fall-asleep-in-the-heat thing) of cooler weather.

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(MORE: Dew point vs. relative humidity explained)

Another thing to remember is that those are real temperatures, not feels-like temperatures. Humidity can drive up the heat index and contribute to your body’s struggles to cool itself, whether the weather is in the ideal temperature range or not.

Enjoy it while you can

Unfortunately, the hours with perfect temperatures for sleeping are getting harder to come by. 

A new analysis from Climate Central found that people are losing an average of 56 hours of sleep per year because of high temperatures globally, and climate change is making things worse.

Across the U.S., people have lost on average up to 10 hours of sleep each year from 2020 to 2025 because of climate change, according to Climate Central, and while it may not seem like a lot, every hour counts.

Even if you aren’t losing sleep, the quality of your sleep can still be negatively affected by high temperatures. And the worse the heat, the worse your sleep.

How it works:

Your circadian rhythm, the way your body naturally tells time and knows when to sleep and when to wake, causes your body to cool every night. 

That cooling process actually starts about two hours before you usually go to bed (hence the importance of a consistent sleep schedule), and it helps let your brain know that it’s time to go to sleep.

By keeping your bedroom cool, it makes it easier for your body to cool itself off. It also helps your body maintain that cooler temperature so you can fully recharge your internal batteries.

What you can do differently:

If you don't have reliable air conditioning or you just want to save some money on your monthly electric bill, there are a few different things you can do to help keep your bedroom cool.

• Keep your windows and curtains closed during the day to insulate your bedroom from the heat outside.
• Open windows at night on opposite sides of the room to create a breeze, or use a window fan to draw in cooler air outside.
• Use a ceiling fan or portable fan, and make sure it's spinning the correct direction. When it's hot out, your ceiling fan should be spinning counterclockwise.
• Stick with breathable, cooling and lightweight fabrics for your bedding and pajamas.
• Use a dehumidifier if the humidity is making things uncomfortable.

Sara Tonks is an avid fan of sleep and a content meteorologist with weather.com and has a bachelor’s and a master’s degree from Georgia Tech in Earth and Atmospheric Sciences, along with a master’s degree from Unity Environmental University in Marine Science.