The ideal room temperature for a newborn is between 68°F and 72°F (20°C to 22°C). This range keeps most babies comfortable without raising the risk of overheating, which is a known factor in Sudden Infant Death Syndrome (SIDS). The American Academy of Pediatrics doesn’t specify an exact number but offers a practical rule: your baby needs only one more layer than you would wear to be comfortable in the same room.
Why Temperature Matters for Newborns
Newborns can’t regulate their body temperature the way adults can. Their thermoregulatory system is still developing, which means they’re more vulnerable to both heat and cold. When a room is too warm, a baby’s body has to work harder to cool down, and this thermal stress can impair arousal mechanisms, respiratory drive, and heart responses during sleep. In short, an overheated baby may not wake up or respond normally to breathing disruptions, which is why overheating is considered a risk factor for SIDS.
On the other end, a room that’s too cold forces a newborn to burn extra calories and oxygen just to stay warm. That energy expenditure competes with the energy a baby needs for growth and essential organ function. Prolonged cold stress can worsen respiratory distress and cause blood sugar to drop. While mild coolness is generally less dangerous than overheating, it’s still worth avoiding.
How to Tell If Your Baby Is Too Warm
A room thermometer is helpful, but your baby’s body gives you the most reliable feedback. Touch the skin on their chest, belly, or the back of their neck. These areas reflect core temperature better than hands or feet, which tend to run cool in newborns regardless of room temperature. Skin that feels hot or clammy means your baby is likely overdressed or the room is too warm.
Other signs of overheating include:
- Sweating or damp hair, though some babies overheat without visible sweat
- Flushed or red skin, especially on the face and chest
- Rapid breathing or restlessness during sleep
- Heat rash, which looks like tiny red bumps in skin folds, around the neck, or on the bottom
The AAP specifically advises against putting a hat on your baby indoors once you’re home from the hospital. Babies lose a significant amount of heat through their heads, and a hat in a warm room can easily tip them into overheating territory.
Dressing Your Baby for Sleep
The one-layer-more rule is the simplest guide. If you’re comfortable in a T-shirt, your baby is fine in a onesie plus a light sleep sack. If you need a sweater, add a warmer layer for the baby. Loose blankets, quilts, and comforters should never go in the crib, so wearable blankets (sleep sacks) are the safest way to add warmth.
Sleep sacks are rated by TOG, a measure of thermal resistance. The higher the TOG number, the warmer the garment. Here’s a general guide:
- 0.2 TOG: Best for rooms between 75°F and 81°F (very warm nights)
- 1.0 TOG: Best for rooms between 68°F and 75°F (the typical comfort zone)
- 2.5 TOG: Best for rooms between 61°F and 68°F (cooler rooms)
- 3.5 TOG: Best for rooms below 61°F
If you’re unsure which TOG to choose, err on the lighter side. It’s easier and safer to add a layer underneath than to risk overheating with a heavier sleep sack.
Air Circulation and Fan Use
Good airflow helps keep the temperature around your baby consistent and prevents pockets of warm, stale air from forming near their face. A study published in the Archives of Pediatrics & Adolescent Medicine found that using a fan during sleep was associated with a 72% reduction in SIDS risk. The fan doesn’t need to blow directly on your baby. A ceiling fan on low or a standing fan pointed toward a wall is enough to keep air moving.
If you’re using air conditioning or heating, place the crib at least two feet away from vents, windows, and radiators. Drafts from vents can create localized hot or cold spots that don’t match what your room thermometer reads. Keeping the crib away from windows also avoids temperature swings from sunlight or cold glass.
Humidity in the Nursery
Temperature is only part of the equation. The ideal humidity level for a nursery sits between 35% and 50%. Air that’s too dry can irritate your baby’s nasal passages, cause dry skin, and make breathing less comfortable. This is especially common in winter when heating systems strip moisture from indoor air. A simple cool-mist humidifier can bring levels into range, and an inexpensive hygrometer (humidity gauge) lets you monitor it.
Humidity above 50% creates a different problem: it encourages mold growth and dust mites, both of which can affect a baby’s breathing. If your home runs humid, a dehumidifier or running the air conditioner periodically can help.
Seasonal Adjustments
In summer, keeping a nursery at 68°F to 72°F may require air conditioning or a fan. Dress your baby in just a diaper and a light 0.2 TOG sleep sack on the hottest nights. If you don’t have air conditioning, a fan can lower the perceived temperature and improve safety at the same time.
In winter, the challenge flips. Heated homes can easily push past 72°F, especially in small bedrooms with the door closed. Keep the thermostat set to 68°F to 70°F overnight if possible, and resist the urge to pile on layers. A footed pajama under a 1.0 or 2.5 TOG sleep sack is plenty for most winter nights in a heated home. Check your baby’s chest before you go to bed and again if you wake during the night. Warm and dry means they’re comfortable. Hot or damp means you should remove a layer.