June in London. Sunset at 9:21pm. Twilight until past 10pm. Sunrise at 4:45am. If your sleep was already fragile in winter, summer is the season that breaks it.
The instinct is to reach for blackout curtains. They help. They are not the whole picture.
The actual disruptor
Outdoor light at 9pm only matters if your eyes are seeing it. Curtained off, screen on, lamps on, the bigger source of evening light is your own room. A 60-watt overhead bulb and a phone screen put more melanopic light into your eyes than the bedroom window does after sundown.
This is why people who do their wind-down correctly sleep through long summer evenings without trouble. The room is doing the work, not the curtains.
What to actually change
Three things, in order.
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The room. Switch overhead lights for warm bulbs or off entirely after dinner. An Amber Sleep Bulb in the bedroom lamp is the simplest single move. Once the room is properly dim and warm, the late evening outside the window matters much less.
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The screen. Phone, laptop, TV. If you are watching something, Orange Lens Glasses work fine for two hours of viewing without disrupting colour enough to bother you. The melatonin protection in summer is the same as in winter. Your body still needs the signal.
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The curtain. Blackout curtains, eye mask, or both. The 5am light leaking in is the most underrated cause of summer waking. Even a thin shaft of bright morning across the room is enough to lift you from REM thirty minutes earlier than you wanted.
Shift workers doing summer nights
Particular case. If you finish a night shift at 7am in June, you are walking home into peak melatonin-suppressing light. Sunglasses on the walk back are not optional. Once home, full blackout in the bedroom, then sleep into the afternoon if you can.
The hardest part of summer for shift workers is that even one wrong morning exposure can wreck the next sleep window. Be ruthless about it.
The cost-benefit
Curtains: highest yield, especially for waking. £30-£100 once.
Amber bulb: highest yield for the evening, £15 per bulb. Replaces the room without you thinking about it.
Lenses: most flexible. Useful for late screen sessions or for the final hour before bed.
If you only do one thing, get blackout for the bedroom window first. If you do two, add the amber bulb. Most people who try these together find summer sleep stops feeling fragile.
