The safest way to keep a baby warm in a bassinet is with layers of clothing and a wearable blanket, not loose bedding. The ideal room temperature for infant sleep is 16 to 20°C (about 61 to 68°F), which feels slightly cool to most adults. Getting this combination right lets your baby sleep comfortably without the suffocation risks that come with blankets, quilts, or other loose coverings.
Why Blankets Don’t Belong in a Bassinet
The American Academy of Pediatrics is clear on this: keep soft objects like pillows, quilts, comforters, and loose blankets out of the infant sleep area entirely. These items increase the risk of suffocation, entrapment, and strangulation. Instead, the AAP recommends either dressing the infant in layers of clothing or using a wearable blanket to maintain warmth safely.
The same rule applies to hats and beanies during indoor sleep. Babies release excess heat through their heads and faces, so covering them can cause rapid overheating. Headwear can also slip down over a baby’s face, creating a suffocation hazard. Keep your baby’s head uncovered every time they sleep indoors.
Set the Room Temperature First
Before you think about clothing layers, get the room right. A nursery between 61°F and 68°F (16 to 20°C) is the sweet spot recommended by safe sleep organizations. That range might feel cool to you, but babies overheat more easily than adults, and a slightly cool room is safer than a warm one.
If you need a space heater during winter months, place it on a flat, level surface at least three feet from anything flammable, including curtains, furniture, and the bassinet itself. A room thermometer near the bassinet (not right next to the heater) gives you the most accurate reading of what your baby is actually experiencing.
How TOG Ratings Work
TOG is a measure of thermal resistance, essentially how warm a sleep sack will keep your baby. Higher TOG numbers mean more insulation. Matching the right TOG to your room temperature is the simplest way to get warmth right without guessing.
- 0.2 TOG: Best for warm rooms, 75°F to 81°F. This is barely more than a sheet.
- 1.0 TOG: Suits moderate rooms, 68°F to 75°F. A good year-round option in climate-controlled homes.
- 1.5 TOG: Works for slightly cool rooms, 64°F to 72°F.
- 2.5 TOG: Designed for cool rooms, 61°F to 68°F. This is where most winter nights fall.
- 3.5 TOG: For cold environments below 61°F, like older homes with poor insulation.
Most sleep sack brands print the TOG rating on the tag or packaging. If your bassinet is in a bedroom that stays around 68°F, a 1.0 or 1.5 TOG sleep sack paired with a single layer of clothing underneath is a reliable starting point.
Layering Clothing Under a Sleep Sack
A useful rule of thumb: dress your baby in no more than one additional layer than you would need to be comfortable in the same room. If you’d sleep comfortably in a T-shirt, your baby likely needs a onesie plus a sleep sack. If you’d want long sleeves and a blanket, a long-sleeved bodysuit under a higher-TOG sleep sack makes sense.
In a warm room (above 75°F), a short-sleeved onesie or even just a diaper under a lightweight 0.2 TOG sack is enough. In a cool room (61 to 68°F), try a long-sleeved bodysuit with footed pajamas under a 2.5 TOG sack. The goal is to keep your baby’s core warm without piling on so much that they can’t regulate their temperature.
Choosing the Right Bassinet Sheet
The only fabric that should be on the bassinet mattress is a single fitted sheet. Choose one that fits tightly with no bunching, slack, or loose corners. A sheet that pulls away from the mattress during the night becomes a suffocation hazard. Cotton is the most common choice because it breathes well and doesn’t trap excess heat against your baby’s skin. Avoid fleece or flannel sheets in rooms that are already at the recommended temperature range, as these add warmth you may not need.
How to Tell if Your Baby Is Too Warm
Cold hands and feet are normal in newborns and don’t reliably indicate that a baby needs more warmth. The better check is to feel the skin on their chest, back, or the nape of their neck. If that skin feels hot or damp with sweat, your baby is overdressed.
Other signs of overheating include flushed or red skin, rapid breathing, restless or disrupted sleep, and unusual irritability or lethargy. Heat rash, which looks like tiny red bumps, tends to show up around the neck, back, and underarms. A rectal temperature above 100.4°F (38°C) also suggests overheating rather than illness, especially if it drops after you remove a layer.
Overheating is a more common and more dangerous problem than being slightly cool. A baby who is a little chilly will wake up and fuss, which is self-correcting. A baby who overheats faces a genuinely elevated risk of sleep-related complications. When in doubt, go one layer lighter rather than heavier.
Putting It All Together
The system is straightforward once you have the pieces in place. Set your room to 61 to 68°F. Put a tight-fitting cotton sheet on the bassinet mattress with nothing else in the sleep space. Dress your baby in one base layer appropriate for the temperature. Place them in a sleep sack with a TOG rating matched to the room. Leave their head uncovered. Check their chest or neck after 15 to 20 minutes to confirm they feel warm but not hot or sweaty.
Room temperatures shift overnight, especially in homes without central heating. If your bedroom drops significantly between bedtime and early morning, choose clothing and TOG ratings for the coolest temperature the room will reach, not the temperature when you put your baby down. A baby who is slightly warm at 9 p.m. but comfortable at 3 a.m. is better off than one who is comfortable at bedtime and cold by dawn.