Dressing for sleep: the sleep sack era

Medically-informed · Sources: CDC · Updated June 2026 · 3 min read

Why sacks won

Loose blankets are off the table for safe sleep, swaddles retire when rolling starts — the wearable blanket is what remains, and it's genuinely better: warmth that can't cover a face or be kicked off.

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The TOG logic

Sleep sacks come in warmth ratings (TOG). Rough guide: light 0.5–1.0 for warm rooms, 2.5 for cool ones. Room around 68–72°F with a 1.0 sack and one layer underneath is a commonly comfortable default.

Is this normal for your baby?

FirstWeeks answers with your baby’s age and today’s log in mind — with pediatric sources attached.

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The layer math

Dress baby in one more light layer than you'd wear to sleep in that room — then verify by feel: chest or back of neck should be warm, not sweaty. Cool hands lie; ignore them.

Signs you got it wrong

Sweaty neck, damp hair, flushed cheeks — too warm (the riskier direction; overheating matters for safe sleep). Cool chest and fussing at sleep onset — add a layer.

Fit notes

Armholes snug enough that baby can't slide inside the sack; neckline that can't ride over the chin; correct size, not aspirational. Zipper upside-down models win the 3 AM diaper Olympics.