What are the guidelines for morning light exposure?

Get outdoors for bright natural light as soon as you can after waking—ideally within the first 30–60 minutes and before 9 a.m. when possible. This helps anchor circadian timing and supports daytime alertness and sleep later that night. 1 2

• 100,000 lux: Treat this as a target for cumulative morning light exposure, not a brightness to stare into. Bright indoor lighting is far dimmer—about 4,000–5,000 lux in the example given—so outdoor light is preferable. 2 3
• Exposure duration: Aim for about 5 minutes in clear conditions, 10 minutes with cloud cover, and up to 20–30 minutes in dense overcast or rain. 4
• Go outside: Light through a window or car windshield is much less effective; get the light outdoors when possible. 5
• Benefits: Morning light helps time the cortisol rise and supports alertness, focus, mood, and sleep timing—setting a timer to fall asleep about 16 hours later. 6 7
• If you miss a day: Get twice the duration of sunlight the following morning. A Light Meter app can estimate lux in your environment. 8