How to Sleep Well in Summer’s Light: A Functional Guide
Understanding circadian rhythm disruption, melatonin and light exposure, and how to sleep in summer.
Summer is the season of brightness. The long days invite us to do more, stay up later, and say yes to more than we usually do. But for many—especially those with insomnia, burnout, or sensitive nervous systems—summer is when sleep can actually get worse.
The way we are made, we’re not designed for endless daylight. Our ancestors aligned with dawn and dusk, and yet here we are, living in what T.S. Wiley called an “endless summer”—tricked by artificial light into staying “on” all the time.
In this article, I want to share with you why sleep becomes harder in the summer, how artificial light (and even prolonged daylight) and insomnia are intimately connected, and how you can work with light rather than fight it.
Light, Not Melatonin, Runs the Show
Melatonin gets so much attention. This hormone is indeed important, but light is what often regulates your internal rhythms.
As I wrote in The Deep Blue Sleep:
“It is not melatonin that determines our rhythms, it is light.”
Your body receives light cues through the eyes, directly influencing the suprachiasmatic nucleus—the brain’s internal clock. Natural light in the morning triggers a cascade: cortisol rises, energy returns, and your body begins its daily rhythm.
In summer, we get more sunlight—which can be supportive, in theory. But artificial light in the evening—from overhead bulbs, screens, and even tiny LED appliance lights—confuses this system. Your brain no longer knows when day ends.
Also, the longer natural days of summer can shorten your opportunity to go to bed early enough to get sufficient sleep before the strong morning light wakes you again.
As a result of long hours of light (whether natural or artificial):
Melatonin is suppressed
Cortisol stays elevated too late
Sleep onset is delayed
Nighttime becomes restless
Morning waking happens too early
Living in an “Endless Summer” Isn’t Free
T.S. Wiley, in Lights Out: Sleep, Sugar, and Survival, describes this brilliantly:
“We are living in an endless summer. And in summer mode, your body stays alert, stores fat, and forgets how to rest.”
Our biology hasn’t evolved to keep pace with the technology of constant light.
While our brains still seek darkness to restore, when our homes stay lit like it’s midday, your body stays alert, sugar-seeking, and in survival mode.
This can lead to:
Disrupted sleep
Elevated nighttime cortisol
Increased cravings and fat storage
Exhaustion masked by stimulation
As I share in my book:
“We evolved to rest with the darkness. Every light left on at night tells our body to ignore that wisdom.”
This isn’t about perfection or not using lights at all in the evening, but it’s about restoring some contrast, especially with the light already being brighter in the evening in the summer.
Use the Morning Light to Your Advantage
If there’s one functional medicine principle to live by in summer, it’s this: get light early, and limit it late.
Morning Practices to Anchor Your Rhythm:
Step outside within 30 minutes of waking
Avoid sunglasses for the first 10–20 minutes
Move your body gently in the morning light (walk, stretch, sun-gaze)
Drink water before caffeine
Eat 20 to 30 grams of protein for breakfast.
Wait 60–90 minutes before coffee to support your cortisol awakening response (Read more →)
This early light helps anchor your circadian rhythm and supports better melatonin production later in the evening.
How to Wind Down When It’s Still Bright Out
This is where most people struggle. The sun hasn’t set, the house is lit up, and you’re catching up on texts or dishes, or scrolling to relax. But if you want to sleep well in summer, you need to cue your system that night has begun—even if it’s still light outside.
Evening Sleep Hygiene Rituals:
Dim lights 1–2 hours before bed—use low lamps, amber bulbs, or candlelight
Eliminate blue light: screens, LED alarm clocks, TV backlighting, smart devices
Filter your environment: cover appliance lights, install red light filters on phones, or consider blue-blocking glasses
Let your body feel the darkness: use blackout curtains, wear an eye mask, avoid overhead lighting after 8pm
Unwind with rhythm: choose a consistent wind-down flow (herbal tea, warm bath, light reading, journaling)
These small cues signal to your nervous system: we’re powering down now.
Functional Medicine Meets Sleep Foundations
In functional medicine, we look upstream. We don’t just patch insomnia—we explore its roots.
We ask:
What systems are out of sync?
What hormonal or nervous system patterns need restoring?
What rhythms have been overridden by modern life?
So many of my patients are craving rest and they want restoration that makes sense in their real lives.
The Deep Blue Sleep was born from this very need: to understand how to sleep well again by working with your body’s natural rhythms—not against them.
📘 Explore The Deep Blue Sleep book if you want to go deeper into the physiology and healing of sleep.
💛 Or schedule a free sleep consult if you're ready for care that listens to your whole system.
