Yes, by the published categories: WHO’s Table 1 places 6 at the bottom of the High band (6 to 7). It is the first reading on the scale that carries that label.

WHO category: High (6 to 7)

How long to burn in UV 6?

At UV index 6, the erythemal-dose model computes a first-perceptible-reddening reference dose after roughly 22 minutes of continuous unprotected exposure for Fitzpatrick skin type I, and roughly 111 minutes for type VI. The full type I–VI table is below, with the arithmetic and the sources.

Computed from a dose rate of 5.4 standard erythema doses per hour at UV index 6. Reference values, not measurements of any individual.
Fitzpatrick skin type	Reference dose to first erythema (SED)	Minutes to that dose at UV 6	0.6 × that figure (min)
Type Ialways burns, never tans	2	22	13
Type IIusually burns, tans minimally	2.5	28	17
Type IIIsometimes mild burn, tans uniformly	3.5	39	23
Type IVburns minimally, always tans well	4.5	50	30
Type Vvery rarely burns, tans easily	6	67	40
Type VIdeeply pigmented, never burns	10	111	67

The fourth column is a fixed 0.6 multiple of the third — an arithmetic margin for the roughly ±30–50% spread in published reference doses within one phototype. It is what the app reports.

“Reporting burn times is not recommended.”

— WHO, WMO, UNEP and ICNIRP, Global Solar UV Index: A Practical Guide, WHO/SDE/OEH/02.2 (2002)

The guide gives its reasoning directly: “people tend to interpret burn times to mean that there is a safe level of unprotected sun exposure”, and relating index values to a time to burn therefore “sends out the wrong message”.

Why we publish the figure anyway →

This page answers the UV 6 question. The app answers yours.

Real days do not sit at 6 — the index climbs to a peak and falls again. Safe Sun Window takes your skin type and the index where you actually are, and runs this same calculation on those inputs. Free, no account, no ads. Return visits are counted with a random first-party id that goes to no one else. If you turn on location, your device rounds your position to about 10 km before it reaches our weather provider for the UV reading, with no id attached.

Open Safe Sun Window →

What UV 6 means

Six opens WHO’s High band (6 to 7). It is also the cleanest arithmetic on the whole scale: 6 is exactly twice 3, so at UV 6 erythemal dose accumulates at exactly twice the UV 3 rate and every modelled threshold in the table below is exactly half its UV 3 value.

That exact halving is a property of how the index is defined, not a rule of thumb. WHO’s Annex C gives the index as 40 m²/W multiplied by the erythemally weighted irradiance, integrated against the CIE reference action spectrum for UV-induced erythema (ISO 17166:1999 / CIE S 007/E-1998). Linear in, linear out.

Where and when UV 6 actually occurs

Six needs a genuinely high sun, or a lower sun with altitude making up the difference. Readings of 6 typically come from:

Clear-sky midday at mid-latitudes through late spring and early autumn.
Roughly an hour either side of solar noon on a mid-latitude summer day.
Midday for most of the year outside winter across the subtropics.
Alpine and snowfield locations in spring, where WHO’s 10–12%-per-1000-metres altitude effect lifts a base reading that would otherwise sit in the Moderate band.

Six is typically an inside-the-window reading. WHO puts the daily maximum in the four-hour period around solar noon, and notes that solar noon itself falls between local noon and 2 p.m. depending on where you sit in your timezone and whether daylight saving is in force — so a 6 recorded at “midday” by the clock may not be the day’s peak.

The six factors WHO lists as setting the index, with its own figures →

What the published guidance says at UV 6

The US EPA groups 6 in the range it labels “Moderate to High” and publishes for it: “Protection needed. Seek shade during late morning through mid-afternoon. When outside, generously apply broad-spectrum SPF-15 or higher sunscreen on exposed skin, and wear protective clothing, a wide-brimmed hat, and sunglasses.”

WHO’s guide notes that shade can reduce UV by 50% or more, and that indoor workers receive only 10% to 20% of outdoor workers’ yearly UV exposure — both are statements about where the dose comes from, not about how long anyone may remain outside.

The published scheme is binary, not graded: the same measures apply from UV 3 upward, and what changes with the index is the rate at which erythemal dose accumulates. Why the scheme is not graded →

Check the arithmetic

At UV 6, an hour of continuous exposure delivers 6 × 0.9 = 5.4 standard erythema doses. Fitzpatrick type II’s reference dose is 2.5 SED, so 2.5 ÷ 5.4 × 60 = 28 minutes. Every row in the table above is that division with a different reference dose.

The 0.9 factor is exact, and follows from the definition of the index; the reference doses are not. Where the 0.9 comes from, and what the reference doses are →

Questions

How long to burn in UV 6?: At UV index 6 the model computes a first-erythema reference dose in about 22 minutes of continuous unprotected exposure for Fitzpatrick type I skin and about 111 minutes for type VI. These are computed model outputs for a reference dose, not durations of demonstrated safety.
Is UV 6 high?: Yes, by the published categories: WHO’s Table 1 places 6 at the bottom of the High band (6 to 7). It is the first reading on the scale that carries that label.

Other UV levels

All levels, the full method, and why burn times are contested →

Sources for the figures above

World Health Organization, World Meteorological Organization, United Nations Environment Programme and International Commission on Non-Ionizing Radiation Protection. “Global Solar UV Index: A Practical Guide.” WHO/SDE/OEH/02.2, 2002.
ISO 17166:1999 / CIE S 007/E-1998. Erythema reference action spectrum and standard erythema dose.
United States Environmental Protection Agency. “UV Index Scale.” epa.gov, last updated 15 June 2026; verified 3 August 2026.
Fitzpatrick TB. “The validity and practicality of sun-reactive skin types I through VI.” Archives of Dermatology, 1988;124(6):869–871.
Minimal-erythema-dose values per Fitzpatrick phototype — working reference values, range-checked against ISO 17166:1999; the six-value progression itself is not traced to a named primary document.

Full annotated source list, with what each one is used for →