UV Index Guide: What the Numbers Mean for Your Skin
The UV index is a scale from 0 to 11+ that measures the strength of ultraviolet radiation from the sun at your location. Higher numbers mean greater risk of sunburn and skin damage. But the UV index alone doesn't tell the full story — your skin type determines how quickly you'll actually burn. If you want to see the UV index on your phone right now, read our guide on how to check the UV index on iPhone.
UV index scale explained
UV 0–2 — Low
Minimal risk for most people. You can safely enjoy the outdoors without sunscreen for extended periods. Fair-skinned individuals (Fitzpatrick Type I–II) may still want to apply SPF 30+ if spending more than an hour outside.
UV 3–5 — Moderate
Unprotected sun exposure can cause sunburn in 30–45 minutes for fair skin. Wear sunscreen, a hat, and sunglasses during midday hours. Darker skin tones (Type IV–VI) can generally spend longer outside but should still take care.
UV 6–7 — High
Sunburn can occur in under 20 minutes for fair skin. Seek shade during peak hours (10 AM – 4 PM), wear protective clothing, and reapply SPF 30+ sunscreen every two hours.
UV 8–10 — Very High
Skin damage happens fast — fair-skinned people can burn in as little as 10 minutes. Limit midday outdoor time, cover up, and use SPF 50+ sunscreen. Even darker skin tones should take precautions at these levels.
UV 11+ — Extreme
Maximum risk. Avoid direct sun exposure during midday hours if possible. If you must be outside, wear long sleeves, a wide-brim hat, and SPF 50+ sunscreen — regardless of skin type.
How skin type affects your burn time
The Fitzpatrick scale classifies skin into six types based on how it reacts to UV exposure. Knowing your type helps you understand how long you can safely stay in the sun without protection — which is exactly what a personalized UV forecast app like Sunwise calculates for you automatically. Not sure which type you are? Take the Fitzpatrick skin type quiz — it walks through the standard skin phototype questionnaire with a scoring rubric.
| Type | Description | Approx. Burn Time |
|---|---|---|
| I | Very fair skin, light eyes, always burns, never tans | ~10 min at UV 10 |
| II | Fair skin, burns easily, tans minimally | ~15 min at UV 10 |
| III | Medium skin, sometimes burns, tans gradually | ~20 min at UV 10 |
| IV | Olive skin, rarely burns, tans easily | ~30 min at UV 10 |
| V | Brown skin, very rarely burns, tans darkly | ~45 min at UV 10 |
| VI | Very dark skin, almost never burns | ~60 min at UV 10 |
Why a generic UV index isn't enough
Most weather apps show a single UV index number for your area. But a UV index of 6 means very different things for someone with Type I skin versus Type V skin. A person with very fair skin could burn in 15 minutes at UV 6, while someone with darker skin might be safe for over an hour.
That's why Sunwise pairs the UV index forecast with your personal skin type to calculate an actual burn time — giving you a specific, actionable number instead of a vague risk level. Whether you're checking the UV index from your iPhone, iPad, a Home Screen widget, or the UV index on Apple Watch, you always know exactly how long you can safely spend in the sun. If you're comparing options, see our roundup of the best UV index apps for iPhone.
Try Sunwise
Sunwise is a free UV forecast app for iPhone, iPad, and Apple Watch that delivers personalized burn times based on your skin type. It includes hourly and 7-day UV index forecasts, Apple Watch complications, Home Screen widgets, and Siri integration.
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