UV Index Scale Explained (0–11+)

The UV Index Scale at a Glance

The UV index is a 0-to-11+ scale developed by the World Health Organization and the World Meteorological Organization. Each step on the scale corresponds to a specific level of biological harm potential, with clear protective recommendations attached. The EPA UV Index Scale formalises the U.S. version and is used as a global reference.

This guide walks through every level on the scale, what it means for skin and eyes, and exactly how to respond.

UV Index 0 — Night / No UV

UV 0 indicates no measurable UV radiation, typically at night or just before dawn / after dusk. No protection needed.

UV Index 1 — Minimal

Just after sunrise or before sunset on most days. Burn risk is essentially zero for all skin types. Sunglasses optional. See our full UV Index 1 guide.

UV Index 2 — Low

Common winter daytime values in temperate cities like London or Berlin. Low risk for most. People with very fair skin (Fitzpatrick I) or photosensitive conditions should consider basic protection. See UV Index 2 guide.

UV Index 3 — Moderate (Protection Begins)

The first official threshold for active protection. Fair skin (types I–II) can burn in 30–45 minutes. Recommendations:

SPF 30 broad-spectrum sunscreen on exposed skin.
Sunglasses for eye protection.
Hat for extended outdoor time.

This is the level most temperate cities reach on a clear spring or autumn day. See UV Index 3 guide.

UV Index 4 — Moderate

Burn time for fair skin drops to 25–30 minutes. Same recommendations as UV 3, with reapplication after 2 hours of outdoor time. See UV Index 4 guide.

UV Index 5 — Moderate to High

The upper bound of "moderate". Burn time for fair skin: 20–25 minutes. Common in temperate cities in late spring and early autumn, and tropical destinations during cloudier months. See UV Index 5 guide.

UV Index 6 — High

A significant escalation. Burn time for fair skin drops to 15–20 minutes. Recommendations:

SPF 30+ sunscreen, applied 15 minutes before going outside.
Wide-brim hat (4"+ brim).
UV400 sunglasses.
Seek shade between 10 a.m. and 4 p.m.

Common in temperate cities at the height of summer and in tropical destinations year-round during early/late hours. See UV Index 6 guide.

UV Index 7 — High

Burn time for fair skin: 12–15 minutes. The threshold at which most public health bodies, including CDC sun safety, recommend active midday avoidance. See UV Index 7 guide.

UV Index 8 — Very High

Serious risk threshold. Fair skin burns in under 10 minutes. Recommendations:

SPF 50 broad-spectrum sunscreen.
UPF 50+ long-sleeve clothing for extended outdoor time.
Wide-brim hat.
UV400 sunglasses.
Avoid midday outdoor exposure where possible.

Common in tropical destinations like Bangkok and Cancún, and high-altitude or southern-hemisphere cities like Sydney in summer. See UV Index 8 guide.

UV Index 9 — Very High

Burn time for fair skin: 7–10 minutes. Same protection profile as UV 8 with shorter reapplication intervals (every 80–90 minutes during outdoor time). See UV Index 9 guide.

UV Index 10 — Very High

Burn time for fair skin: under 8 minutes. The boundary between "very high" and "extreme". Outdoor midday activity should be minimised. Mineral sunscreen reapplied every 80 minutes during water activities. See UV Index 10 guide.

UV Index 11 — Extreme

Burn time for fair skin: 5–7 minutes. Common in equatorial cities like Singapore and high-altitude tropical cities like Quito. Recommendations:

Avoid midday outdoor exposure entirely if possible.
SPF 50, full UPF clothing kit, hat, sunglasses when outside.
Schedule outdoor activities for sunrise or after 4 p.m.

See UV Index 11 guide.

UV Index 12 — Extreme

Burn time for fair skin: 3–5 minutes. Increasingly common at equatorial high-altitude cities and during southern-hemisphere summers. Treat as UV 11+ with maximum protection discipline. See UV Index 12 guide.

UV 13–14 (Off-Scale Extreme)

Although the WHO scale formally tops out at 11+, real-world readings of 13–14 are now routinely measured at high-altitude tropical cities like La Paz, Cusco and parts of the Bolivian and Ecuadorian highlands. Treat these as "absolute maximum" exposure: minimise all outdoor activity during peak hours. The Cancer Council Australia publishes detailed guidance on extreme-UV environments.

How to Use the Scale Day to Day

Check the live UV at your location each morning using Daily UV Tracker.
Match the reading to its tier above.
Combine with your Fitzpatrick skin type to produce a personal burn-time estimate.
Plan outdoor activities around the daily UV peak — see our best times to avoid sun exposure guide.
Pack appropriately using our UV travel checklist.

Authoritative References

Key Takeaways

The UV index scale is a globally standardised, science-backed tool that converts atmospheric UV intensity into clear, level-by-level guidance. Memorise the broad tiers — moderate begins at 3, high at 6, very high at 8, extreme at 11+ — and pair daily readings with your personal skin type and protection level. Done consistently, this single habit becomes one of the highest-leverage skin-health interventions available.

For deeper context on the topics covered above, the following resources expand on the data, science and practical guidance referenced throughout this article. Daily UV Tracker pulls forecast data from established meteorological providers and aligns its risk thresholds with the international standards defined by the World Health Organization, the United States Environmental Protection Agency and the National Oceanic and Atmospheric Administration. Reading the source material directly is the best way to build a working understanding of how ultraviolet radiation behaves, how skin reacts to sustained exposure, and why a daily UV check is one of the highest-leverage habits for long-term skin health.

How to apply this in practice

The single most effective change most readers can make is to fold a UV check into the same morning routine as the weather forecast. Open Daily UV Tracker, note the day's peak UV value and the time it occurs, and choose an outdoor window that sits comfortably outside that peak. On days flagged as very high or extreme, treat shade, broad-spectrum SPF 30+, UPF clothing and wraparound sunglasses as non-negotiable rather than optional. When travelling, repeat the exercise the night before arrival so you are not caught out by an unfamiliar UV climate. Combined with the sources listed above, this habit converts an invisible risk into a set of small, repeatable decisions that compound into meaningful long-term skin protection.