--- title: "Sunscreen on Cloudy Days: Yes, Here's Why" description: "UVA rays penetrate clouds and glass year-round. Learn why daily SPF is essential regardless of weather." lang: en json-ld: | [ { "@context": "https://schema.org", "@type": "FAQPage", "mainEntity": [ { "@type": "Question", "name": "Sunscreen is only necessary when it is sunny or you are outdoors.", "acceptedAnswer": { "@type": "Answer", "text": "UVA rays penetrate clouds and glass year round and are the primary cause of premature aging. Daily SPF is necessary regardless of weather or whether you are indoors." } } ] }, { "@context": "https://schema.org", "@type": "BreadcrumbList", "itemListElement": [ { "@type": "ListItem", "position": 1, "name": "Home", "item": "https://schoolofdermatology.com/" }, { "@type": "ListItem", "position": 2, "name": "Myth vs Fact", "item": "https://schoolofdermatology.com/myth-vs-fact" }, { "@type": "ListItem", "position": 3, "name": "You Only Need SPF on Sunny Days", "item": "https://schoolofdermatology.com/myth-vs-fact/spf-only-on-sunny-days" } ] } ] --- [![School of Dermatology](/assets/logo-AGZDufdq.svg)](/) Articles [Skin Types](/skin-types) Tools [Glossary](/glossary) ![You Only Need SPF on Sunny Days](https://images.unsplash.com/photo-1532938911079-1b06ac7ceec7?w=800&h=400&fit=crop&fm=webp) [Myth vs. Fact](/myth-vs-fact) # You Only Need SPF on Sunny Days MYTH By Jamie Reeves, Licensed Esthetician June 22, 2024 5 min read ## The Claim "Sunscreen is only necessary when it is sunny or you are outdoors." ## The Science UVA rays, which are responsible for the majority of premature skin aging, photoaging, and increased skin cancer risk, penetrate through clouds and glass. On a cloudy day, up to 80% of UV radiation still reaches the earth's surface. This means your skin is being damaged even when you cannot see or feel the sun. UVA rays also penetrate standard window glass, which is why dermatologists recommend wearing sunscreen even when spending the day indoors near windows. This is particularly relevant for people who work near windows or drive frequently — cumulative UVA exposure through car windows is a well-documented cause of asymmetric photoaging. The distinction between UVA and UVB is important here. UVB rays cause sunburn and are partially blocked by clouds and glass. UVA rays cause deeper, more insidious damage — breaking down collagen, causing hyperpigmentation, and increasing cancer risk — and they are present year-round, in all weather conditions. Daily broad-spectrum SPF 30 or higher is considered non-negotiable by virtually every dermatologist. Beyond sun protection, proactive skin health treatments like LED light therapy have strong research backing for reducing the cumulative effects of UV damage including collagen breakdown and uneven skin tone. Learn more at School of Dermatology's [light therapy resource](https://ledmask.schoolofdermatology.com). ### Key Takeaway UVA rays penetrate clouds and glass year round and are the primary cause of premature aging. Daily SPF is necessary regardless of weather or whether you are indoors. ## Related Articles [ ![What Happens to Your Skin If You Never Wear Sunscreen](https://images.unsplash.com/photo-1532938911079-1b06ac7ceec7?w=800&h=400&fit=crop&q=80&fm=webp) Treatments ### What Happens to Your Skin If You Never Wear Sunscreen Sunscreen isn't a skincare nice-to-have. It's the single most effective anti-aging and cancer-prevention tool available. Here's the science of what happens without it. Jamie Reeves · 9 min read ](/articles/treatments/what-happens-without-sunscreen)[ ![Hyperpigmentation: The Difference Between PIE and PIH](https://images.unsplash.com/photo-1522337360788-8b13dee7a37e?w=800&h=400&fit=crop&q=80&fm=webp) Skin Concerns ### Hyperpigmentation: The Difference Between PIE and PIH That dark spot left behind after a breakout — is it PIE or PIH? The distinction matters more than you think, because the treatments are completely different. Jamie Reeves · 8 min read ](/articles/skin-concerns/hyperpigmentation-pie-vs-pih)[ ![How Retinol Actually Works (And Why Most People Use It Wrong)](/assets/retinol-hero-brmhCd6T.webp) Ingredients ### How Retinol Actually Works (And Why Most People Use It Wrong) Retinol is the most studied anti-aging ingredient in dermatology. But most people either use it wrong or give up too soon. Here's what the science actually says. Jamie Reeves · 9 min read ](/articles/ingredients/how-retinol-actually-works) #### Ingredients - [Browse All](/topics/ingredients) #### Treatments - [Browse All](/topics/treatments) #### Skin Concerns - [Browse All](/topics/skin-concerns) #### Light Therapy - [Browse All](/topics/light-therapy) #### Skin Care - [Browse All](/topics/skin-care) #### Hair Care - [Browse All](/topics/hair-care) #### Resources - [Skincare Glossary](/glossary) - [All Articles](/articles) - [Contact Us](/contact) © 2026 School of Dermatology. All rights reserved. For educational purposes only. 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