Sleeping with air conditioning: good or bad for sleep?
When nights get hot, air conditioning can turn an overheated bedroom into a comfortable one. But should it stay on all night? What temperature is reasonable? And what about dry throat, cough or children?
Why an overheated bedroom can disrupt sleep
Sleep is accompanied by changes in thermoregulation. When the environment stays very hot, the body has more difficulty dissipating heat and sleep becomes more fragile. In a controlled study, sleeping at 35 °C reduced total sleep time and increased wakefulness compared with a 20 °C condition. View the study.
More recent real-world data point in the same direction. A longitudinal home study in older adults found sleep to be more efficient and restful when nighttime bedroom temperature was around 20–25 °C in that specific population, with a clinically relevant decline as temperature rose from 25 to 30 °C. See Baniassadi et al.. This is not a universal prescription; it mainly shows that excessive heat is harmful and that comfort ranges vary between individuals.
What temperature should you set the AC to for sleep?
Popular advice often gives a single number such as 18, 19 or 20 °C. Research does not justify turning one of those values into a rule for everyone. Perceived temperature depends on bedding, clothing, humidity, air movement, age and individual physiology.
High nighttime heat increases wakefulness and can disrupt deep and REM sleep under very hot experimental conditions.
An aggressive setting can create discomfort, shivering or awakenings if your bedding and clothing do not match the environment.
A practical target is therefore a room that feels comfortably cool without making you cold while lying still. If you wake because you are chilled, the setting is too low for you even if a website calls that number “ideal.”
Can you leave air conditioning on all night?
For a healthy adult, there is no general reason that AC must be turned off after a fixed number of hours. A stable environment may be more comfortable than cooling the room aggressively and then letting it heat back up enough to trigger sweating and awakenings.
A small randomized crossover trial published in 2025 compared convection air cooling with radiant cooling at a room temperature of 26 °C. It involved only seven healthy women, so it cannot define the best system or temperature for everyone, but it reinforces that cooled sleep environments can be studied without treating air conditioning itself as inherently harmful. See Park et al., 2025.
In practice, a sleep mode, moderate set point or stable thermostat is often more sensible than an extreme “very cold, then completely off” cycle.
Can AC dry your throat, trigger cough or irritate your eyes?
Air conditioning may lower indoor humidity when water vapor condenses on the cooling coil. That can be helpful in a hot, humid room but uncomfortable when the air is already dry. Controlled-environment experiments show that very low humidity increases tear evaporation and worsens several tear-film measures. See Abusharha & Pearce.
Dry air can plausibly worsen throat or nasal irritation in susceptible people, but persistent nighttime cough should not automatically be blamed on AC. Asthma, allergic rhinitis, reflux, infection and other conditions can produce similar symptoms. Ongoing cough, shortness of breath, chest pain or fever deserves a separate explanation.
Should you avoid cold air blowing directly on your face?
Air movement increases heat exchange and can amplify the sensation of cooling. A cold jet blowing directly at the face or upper body for hours may leave some people feeling chilled or irritated. This does not mean airflow itself “causes a cold.”
A simple adjustment is to angle the vents so that cool air mixes through the room rather than hitting the bed directly, and to reduce fan speed once the room has cooled.
Can a poorly maintained AC system cause problems?
Yes, but the issue is then maintenance and indoor air quality rather than cold temperature. Studies of building ventilation systems have linked some forms of moisture or contamination in cooling systems with more respiratory or mucous-membrane symptoms. In EPA BASE data, lack of cleaning of some cooling-system components was associated with increased symptoms. See the study.
At home, follow the manufacturer’s schedule: clean or replace filters, avoid stagnant condensate, investigate unusual smells and service the unit when needed.
Air conditioning, children and babies
For infants, the main goal is to avoid overheating while following safe-sleep guidance. The American Academy of Pediatrics does not specify one room temperature that applies to every infant. It advises caregivers to consider ambient temperature when dressing the baby, avoid overbundling, and watch for signs of overheating such as sweating, flushed skin or a hot chest. See AAP guidance.
AC can therefore be used to keep an overheated room comfortable, but cold airflow should not be aimed directly at the baby and extra layers should not be added automatically just because the AC is on.
Reasonable overnight settings
| Problem | Practical adjustment |
|---|---|
| You still feel hot | Cool the room gradually instead of immediately choosing a very low set point. |
| You wake up cold | Raise the set point slightly or reduce airflow. |
| Dry eyes or throat | Avoid direct airflow, check humidity and avoid overcooling. |
| Noise disturbs sleep | Use sleep mode or a lower fan speed. |
| Allergy symptoms or odor | Clean filters and have the unit inspected if needed. |
If you are deciding between AC and a fan, read our guide on sleeping with a fan on. If the room is comfortable but you still cannot fall asleep, see why you can feel tired and still be unable to sleep.
Frequently asked questions
Is it bad to sleep with AC on all night?
No, not inherently. An overheated bedroom can worsen sleep. The setting becomes a problem mainly when it causes cold discomfort, very dry air, disruptive noise or poor air quality.
What temperature should the AC be at night?
There is no universal number. Aim for a stable, comfortably cool bedroom without feeling cold. A study in older adults found better sleep around 20–25 °C, but that range should not be treated as a rule for every sleeper.
Why does AC make my throat feel dry?
Lower humidity and direct airflow can worsen irritation in some people. Persistent or severe symptoms should prompt consideration of other causes rather than assuming AC is responsible.
Is air conditioning unsafe for a baby?
The main priorities are avoiding overheating and following safe-sleep guidance. Dress the baby for the room conditions, avoid direct cold airflow and do not overbundle.
Key sources
- Baniassadi et al. — Nighttime ambient temperature and sleep in community-dwelling older adults
- Libert et al. — Effect of continuous heat exposure on sleep stages in humans
- Park et al. — Radiant versus convection cooling and sleep
- Abusharha & Pearce — Low humidity and the tear film
- EPA BASE — Ventilation system contamination and respiratory symptoms
- American Academy of Pediatrics — Safe infant sleeping environment