The answer is: nothing. Summer has its own biology, and babies feel it before anyone else.
Why summer disrupts babies’ sleep
Human sleep is regulated by the circadian rhythm, that internal clock that tells the body when it’s day and when it’s night. In babies under 6 months, that clock is still developing. In older babies, it already works, but it is extremely sensitive to light.
Light: the silent enemy of summer sleep
From the summer solstice onward, in Spain the sun rises before 7 a.m. and sets after 9 p.m. That’s 14–15 hours of daylight each day. For a baby’s brain, all that light inhibits melatonin, the hormone that induces sleep. The result: more resistance to going to sleep at night, shorter naps, and earlier wake-ups.
It’s not that your baby has "forgotten" how to sleep. Their biology is simply responding exactly as it should to the light information they receive.
Heat and body temperature
The body needs to lower its core temperature slightly to initiate sleep. When the room is above 22–24°C, that process becomes more difficult. The baby takes longer to fall asleep, wakes more easily, and naps become shorter.
A baby’s ideal sleep temperature is between 18 and 22°C. In summer, maintaining that temperature may require active measures: a fan pointed at the wall, not the baby; lighter sleepwear; airing out the room before bedtime.
Changes to the routine
Vacations, visitors, activities away from home, different mealtimes. Summer disrupts the predictability babies need so much to feel safe. And without predictability, sleep becomes fragmented.
3 adjustments you can make this week
Darken the room with whatever you have
You don’t need a designer blackout blind. A dark blanket secured to the window with painter’s tape works perfectly. The goal is for the room to be dim during naps and for no outside light to enter by bedtime at night. This single change can improve naps within 2–3 days.
Move bath time or the last quiet activity earlier
If your sleep ritual starts at 8 p.m. but there’s still intense light outside, your baby arrives with their nervous system more activated than usual. Moving bath time 20–30 minutes earlier and going into the darkened room sooner helps the body begin lowering its temperature and producing melatonin.
Keep what works
Summer is tempting for changing many things at once. Try changing just one variable per week. If the sleep ritual works—the same song, the same order, the same steps—keep it even if you change the schedule. The sequence is what tells your baby’s brain that sleep is approaching.
A note about summer naps
Naps are summer’s first victims. With more light and ambient noise, babies have more difficulty entering deep sleep during the day. If you see naps shortening to 30–40 minutes, don’t panic: it’s to be expected.
Make sure the room is dark and cool, and observe whether your baby is well-rested even if the nap was shorter. A baby who is cheerful and energetic between naps is getting enough rest, even if the clock says otherwise.
And as for you, Mom
Exhaustion multiplies in summer because nights are more active and naps are shorter. If you feel like you’re at your limit, remember that your nervous system also affects your baby’s sleep. Before going into the room to put your baby to bed, take three mindful breaths. Not to be perfect, but to give your body the signal that it’s time to calm down. Your baby will pick up on it.
Summer doesn’t undo what you’ve built. It only adds external variables that you can manage with small adjustments and an understanding of what’s happening biologically. Your baby hasn’t “gotten worse.” They’re responding to the world with exactly the sensitivity they should have.
The sleep environment designed for the first few months
If your baby is in their first few months of life and you’re looking for a sleep environment that helps them feel contained and secure, even during the most active summer nights, the Starlit Reducer was designed for that particularly fragile first trimester.
Discover the Starlit Reducer
