When and Where You Play in the Sun Matters Most
Time and Place as Modifiers of Personal UV Exposure
Not medical advice. For informational purposes only. Always consult a healthcare professional. Terms
The sun is strongest when your shadow is shorter than you, and most UV hits you during midday — not when it’s hottest. Going on summer vacation to sunny places like Spain gives you way more sunburn risk than being at home. Even underwater, you can get sunburned! But the ocean’s reflection doesn’t add much.
Surprising Findings
Ocean reflection adds less than 0.7 UVI — meaning water doesn’t significantly amplify UV exposure.
Most people think sand and water reflect enough UV to double exposure — but this study shows it’s negligible compared to direct sunlight.
Practical Takeaways
Avoid being outside between 11 a.m. and 3 p.m. on sunny days — especially during holidays — and use your shadow as a real-time UV guide.
Not medical advice. For informational purposes only. Always consult a healthcare professional. Terms
The sun is strongest when your shadow is shorter than you, and most UV hits you during midday — not when it’s hottest. Going on summer vacation to sunny places like Spain gives you way more sunburn risk than being at home. Even underwater, you can get sunburned! But the ocean’s reflection doesn’t add much.
Surprising Findings
Ocean reflection adds less than 0.7 UVI — meaning water doesn’t significantly amplify UV exposure.
Most people think sand and water reflect enough UV to double exposure — but this study shows it’s negligible compared to direct sunlight.
Practical Takeaways
Avoid being outside between 11 a.m. and 3 p.m. on sunny days — especially during holidays — and use your shadow as a real-time UV guide.
Publication
Journal
International Journal of Environmental Research and Public Health
Year
2018
Authors
B. Diffey
Related Content
Claims (2)
Just because it feels hot outside doesn’t mean the sun is strongest—UV rays that cause sunburn peak at noon, but the air keeps getting warmer for hours after. So you can get burned even when it doesn’t feel super hot.
If you're outside in the summer, most of the sun's harmful UV rays hit you between 10 a.m. and 4 p.m., especially around noon—so staying in the shade or indoors during those hours is the best way to cut down on your total sun exposure.