What UV index counts as high?
The 0 to 11+ scale, explained.

A UV index of 6 or 7 is High, 8 to 10 is Very High, and 11 or above is Extreme. Below that, 0 to 2 is Low and 3 to 5 is Moderate. So the moment a reading hits 6, the official scale first calls it High.

That is the short answer. The longer one is worth a minute, because the number on your weather app is doing more work than it looks like. This page lays out the full scale as defined by the World Health Organization and World Meteorological Organization and categorized by the US EPA, what each band actually signals, and one thing the bands quietly assume that trips most people up: the index is a measure of intensity, not a clock.

The full UV index scale

The UV index is an international standard, defined by the World Health Organization together with the World Meteorological Organization, for the strength of sunburn-causing ultraviolet radiation reaching the ground. It starts at 0 and has no fixed top. The US EPA groups the numbers into five named exposure categories, and those five bands are what almost every weather app, news bulletin and beach forecast is referring to when it shows a colour or a word next to the value.

Low: 0 to 2

Minimal danger from the sun for the average person. This is early morning, late evening, deep winter at most latitudes, and overcast days. Public guidance attaches no required protection to this band, though reflective surfaces like fresh snow and open water can still push the effective dose up.

Moderate: 3 to 5

This is the band most people underestimate. The number still sounds small, but 3 is the threshold where the official advice changes: the WHO recommends sun protection from a UV index of 3 upward, and many national weather services issue a sun-protection time starting here. Moderate is not High, but it is the first band where the guidance says to do something.

High: 6 to 7

This is the answer to the question in the title. At 6, the scale first uses the word High. UV at this level reaches a harmful threshold for unprotected skin noticeably faster than at Moderate. On a clear summer day in the temperate world, midday readings commonly land in this band.

Very High: 8 to 10

UV is intense. Public guidance shifts from recommended protection to strongly advising people to limit midday sun and treat shade as essential. Coastal, southern and high-summer locations regularly hit this band at the daily peak.

Extreme: 11 and above

The band has no ceiling. UV accumulates very quickly here. Readings of 11 and beyond turn up at high altitude, close to the equator, and over snow or water that reflects additional UV back up at you. In most populated places the daily peak stays below this, but it is not rare in mountains or the tropics.

What protection each band recommends

The bands exist so that public health bodies can attach the same advice to the same number everywhere in the world. The recommendations below are the public guidance from the WHO and EPA, stated as the general recommendation they are, not as a prescription for any one reader.

• 0 to 2 (Low): no protection required for the average person under normal conditions.
• 3 to 7 (Moderate and High): the WHO and EPA advise seeking shade around midday, covering up with a shirt, a wide-brimmed hat and sunglasses, and applying a broad-spectrum SPF 15 or higher sunscreen to exposed skin.
• 8 and above (Very High and Extreme): extra caution. The guidance is to avoid the sun during midday hours where possible, treat shade as essential, and use clothing, hat, sunglasses and sunscreen together rather than relying on any one of them.

A field shortcut the EPA cites is the shadow rule: if your shadow is shorter than you are, the sun is high and UV is strong, so seek shade; if your shadow is longer than you, UV is easing. It is a rough cue, not a measurement, but it lines up with the curve the index follows across the day.

The number is intensity, not a countdown

Here is the single most useful thing to understand about the scale, and the part the bands do not say out loud. The UV index measures how intense UV is at this moment, not how many minutes you have. A 10 does not mean you have ten minutes. The numbers are roughly linear in intensity, so a UV index of 8 delivers about twice the UV of a 4 over the same stretch of time. A higher number means UV accumulates faster, so the same time outside costs you more, not that a fixed clock has started.

This matters because the index reads the sky, not your skin. As the WHO puts it, higher values mean greater potential for harm and harm occurring sooner, but the index has no way to know your skin, what you are wearing, or what you have already had today. That is why no honest source converts a UV index into a personal safe-tanning time, and why an app should not either. The scale tells you the conditions. What those conditions mean for you is a different question, and it belongs to a dermatologist, not a number.

Seeing your band, right now

Knowing the bands is the methodology layer. The practical question is which band you are in this hour, and how it changes across the day, because UV is not flat: it climbs to a peak around solar noon and falls away on either side. Honest Tan shows the live UV index for your location, hour by hour, drawn straight from Apple WeatherKit with an Open-Meteo fallback, and labels which band you are in right now so you do not have to hold the scale in your head. It plots the day's curve so the High and Very High hours are obvious at a glance, and it does it for free. Reading the real number is one tap away.

For the related questions, see when the UV index is highest during the day and whether cloud, altitude, snow or water change the UV index.

Sources: World Health Organization, Radiation: The ultraviolet (UV) index; US EPA, UV Index Scale 0 to 11+; WHO/WMO/UNEP/ICNIRP, Global Solar UV Index: A Practical Guide. The UV index is a forecast of ground-level conditions; the sky has the final say.