Season Changes and Shallow Sleep: Summer Nights Really Do Sleep Worse

The first hot night of June. You’ve kicked the blanket to the foot of the bed and you’re turning over, and over again. The AC hums on, yet you feel like you were awake all night—and you start to wonder: is my sleep getting worse?

Let me return the verdict first: mostly it’s not you. It’s the weather.

Falling asleep depends on a key: the core body temperature has to drop. Before sleep, the body automatically moves heat from the core out to the limbs—that’s why hands and feet run warm at night: they’re radiating. When the room is too hot and too humid, the key won’t turn: the core can’t come down, sleep arrives slowly; sweat and stale heat mean more tossing and lighter sleep. Summer’s sleep trouble loses at this gate first.

Then there’s the light. Summer days run long: bright before 5 a.m., sun still up at 7 p.m. The light that arrives early in the morning pulls the body clock’s “wake-up bell” earlier—what feels like broken sleep is often just summer waking you ahead of schedule. Put the two together and you get the classic summer combination: slower to fall asleep than in spring, lighter than in winter, total hours quietly shrinking. Long-term sleep research does find this seasonal trend: summer nights run shorter, with later sleep onset.

The good news: both causes have countermeasures.

1. Cool the bedroom first: set the AC between 24–26°C (75–79°F), with a fan moving the air—aim it at the wall or ceiling, not at your body. Even temperature matters more than the exact number.
2. Time the entry right: get the room cold an hour before bed. Falling asleep in a room that’s already cool goes far more smoothly than one cooling down around you—your body gets its “cleared to drop temperature” permit the moment it lies down.
3. Swap the bedding for the season: the thick winter duvet gives way to a light, breathable one; sheets in cotton or linen. The summer goal is “heat escapes easily,” not “withstand the cold.”
4. Upgrade the blackout: when the days stretch, blackout curtains or an eye mask keep the early morning out on the other side of the fabric. (We covered this in “How Dark Should a Bedroom Be?”)
5. Move the shower later: a warm shower one to two hours before bed—water not too hot. Up first, then down: that curve is the ticket into sleep.
6. Drink enough—but schedule it: front-load fluids in the daytime, taper off in the last hour before bed. On summer nights, the bathroom sees more traffic than you’d think.

One gentle reminder: summer sleep is naturally a little shorter and a little lighter than winter’s. That’s the season’s normal breathing, not you falling behind. Don’t grade summer-you by winter’s standards.

If this week has room for one thing: pre-cool the room an hour before bed. That step alone removes most of the tossing on hot nights.

If you’d like to try it in the app: track bedroom temperature alongside the sleep trend for a few weeks—which temperature you sleep deepest at, your data will tell you.

The seasons change the length of the night. They can’t change the body’s wish to rest. All you have to do is open the door and let the cool in.

—By Zhou Xing-Yuan · Former International Flight Crew

A small reminder: Sleep Academy articles offer science explainers and everyday lifestyle suggestions—they are not a substitute for medical diagnosis or treatment. If you’ve been sleeping poorly for a long time, or your sleep problems come with other physical or emotional symptoms, please talk to a doctor or a sleep professional.