The American Academy of Pediatrics recommends keeping the nursery between 68-72°F (20-22°C) for safe infant sleep. This isn’t an arbitrary range — it’s based on research linking overheating to increased SIDS risk and studies showing that sleep quality deteriorates outside this temperature window. Humidity matters too, though it gets less attention: 40-60% relative humidity keeps airways moist, reduces congestion, and inhibits the growth of mold and dust mites that trigger respiratory issues.
Understanding why these ranges matter — and how to maintain them — is one of the simplest ways to improve your baby’s sleep safety and comfort.
Why Temperature Matters: The SIDS Connection
Overheating is a recognized risk factor for Sudden Infant Death Syndrome (SIDS). Multiple studies, including a landmark analysis published in the British Medical Journal, found that infants who died of SIDS were more likely to have been found in overheated rooms or with excessive bedding. The mechanism isn’t fully understood, but researchers believe overheating may impair an infant’s ability to arouse from deep sleep — the protective response that prevents SIDS in most babies.
The risk isn’t limited to extreme heat. A nursery at 76°F with a heavy sleep sack can create the same overheating risk as a nursery at 80°F with lighter clothing. It’s the combination of room temperature, clothing, and bedding that determines the baby’s thermal environment.
Signs of Overheating
Check the baby’s chest or back (not hands or feet, which are often cool even when the baby is warm). Signs of overheating include: sweating (especially on the head and neck), flushed or red skin, rapid breathing, restlessness, and damp hair. If you notice these signs, remove a layer of clothing, reduce the room temperature, or switch to a lighter sleep sack.
Signs of Being Too Cold
A baby who is too cold may have a cool chest or back (not just cool hands), may be fussy or difficult to settle, and may curl into a tight position to conserve heat. Cold stress increases calorie expenditure as the baby works to maintain body temperature, which can affect weight gain in newborns.
The 68-72°F Sweet Spot
At 68°F (20°C): The lower end of the safe range. Appropriate with a standard sleep sack (TOG 1.0-1.5) over a long-sleeve onesie. Some parents find this too cool for their own comfort, but babies sleep well at this temperature because they generate significant body heat relative to their size.
At 70°F (21°C): The middle of the range and the most commonly recommended single temperature. A onesie with a standard sleep sack is typically appropriate. This is the temperature most pediatricians suggest as a starting point.
At 72°F (22°C): The upper end of the safe range. Appropriate with a lighter sleep sack (TOG 0.5-1.0) or a onesie alone. Above 72°F, the risk of overheating increases, especially with any additional layers.
Dressing for the Temperature: TOG Guide
TOG (Thermal Overall Grade) measures the warmth of sleep sacks and blankets. Higher TOG means warmer. Matching the TOG to the room temperature prevents overheating:
Below 64°F (below 18°C): TOG 2.5 sleep sack over a long-sleeve onesie. This temperature is below the recommended range — consider heating the room.
64-68°F (18-20°C): TOG 1.5-2.0 sleep sack over a long-sleeve onesie.
68-72°F (20-22°C): TOG 1.0 sleep sack over a short or long-sleeve onesie. This is the target range.
72-76°F (22-24°C): TOG 0.5 sleep sack over a short-sleeve onesie, or just a onesie. Above 72°F, reduce layers.
Above 76°F (above 24°C): Diaper only, or a diaper with a TOG 0.2 muslin sleep sack. Use a fan for air circulation (not pointed directly at the baby). This temperature is above the recommended range — consider cooling the room.
Why Humidity Matters
Too Dry (Below 40%)
Low humidity dries out the mucous membranes in the nose and throat — the body’s first line of defense against airborne pathogens. In babies, dry nasal passages lead to congestion, difficulty breathing during sleep, nosebleeds, and increased susceptibility to respiratory infections. Dry air also makes eczema and dry skin worse, which is common in infants.
Winter is the primary culprit. Heating systems (forced air, radiators, space heaters) dramatically reduce indoor humidity. A heated home in winter can drop below 20% humidity — well below the 40% minimum. A cool mist humidifier is the standard solution.
Too Humid (Above 60%)
High humidity creates conditions for mold growth, dust mite proliferation, and bacterial growth. Mold spores are a significant respiratory irritant for infants, and dust mites are a leading allergen trigger. Visible condensation on windows is a sign that humidity is too high.
Summer, basements, and poorly ventilated rooms are common high-humidity environments. Air conditioning naturally dehumidifies, but if humidity remains above 60%, a dedicated dehumidifier may be needed.
The 40-60% Target
This range balances airway comfort (above 40%) with mold and dust mite prevention (below 60%). A $10 hygrometer placed at crib level provides accurate readings. Smart hygrometers ($30-$50) send alerts when humidity drifts outside your set range.
Seasonal Challenges and Solutions
Winter
Challenge: Heating dries the air (often below 30% humidity) while maintaining temperature. Solution: Run a cool mist humidifier to maintain 40-50% humidity. Use a programmable thermostat to maintain 68-70°F overnight. Dress the baby in a TOG 1.0-1.5 sleep sack appropriate for the temperature.
Summer
Challenge: High temperatures and humidity. Solution: Use air conditioning to maintain 68-72°F. AC naturally reduces humidity, but monitor with a hygrometer. If humidity drops below 40% from AC, a humidifier may be needed even in summer. Use lighter sleep sacks (TOG 0.5) or just a onesie.
Transitional Seasons (Spring/Fall)
Challenge: Temperature swings between day and night. A room that’s 72°F at bedtime may drop to 64°F by 4 AM. Solution: Use a programmable thermostat to maintain consistent overnight temperature. Dress for the average overnight temperature rather than the bedtime temperature. A nursery thermometer with alerts notifies you of significant temperature changes.
Monitoring Equipment
Basic: A digital thermometer/hygrometer ($8-$10) placed at crib level. Check it before bedtime and during nighttime feedings. The ThermoPro TP49 is accurate and affordable.
Smart: A WiFi-connected sensor ($30-$50) that sends phone alerts when temperature or humidity leaves your set range. The Govee WiFi Thermometer Hygrometer provides continuous monitoring and data logging for around $30-$40.
Integrated: Some baby monitors (Nanit, Arlo Baby, Hatch Rest+) include temperature sensors. Accuracy varies — dedicated sensors are more precise, but integrated sensors are convenient if you already own the monitor.
Common Mistakes
Checking hands and feet: Baby extremities are often cool even when the core is warm. Always check the chest or back for accurate temperature assessment.
Adding blankets: Loose blankets in the crib are a suffocation risk regardless of temperature. Use sleep sacks instead — they provide warmth without the safety risk.
Overcompensating: Parents who are cold themselves tend to overdress the baby. Babies generate more heat per pound of body weight than adults. If you’re comfortable in a t-shirt, your baby is likely comfortable in a onesie and light sleep sack.
Ignoring humidity: Temperature gets all the attention, but humidity affects comfort and health just as much. A room at 70°F and 25% humidity feels different — and affects the baby differently — than 70°F and 45% humidity.
The Bottom Line
Maintain 68-72°F and 40-60% humidity in the nursery. Dress the baby in layers appropriate for the temperature using the TOG guide. Monitor conditions with a thermometer/hygrometer at crib level. Adjust seasonally with a humidifier (winter) or AC/dehumidifier (summer). Check the baby’s chest — not hands — to assess comfort. These simple practices support safe sleep and reduce environmental risk factors for SIDS.