The published schemes do not use that word. WHO classifies 7 as the top of the High band (6 to 7) and describes the index as “an indicator of the potential for skin damage”; the EPA publishes “Protection needed” for the whole 3-to-7 range and changes its wording only at 8.

WHO category: High (6 to 7)

How quickly can you burn in UV 7?

At UV index 7, the erythemal-dose model computes a first-perceptible-reddening reference dose after roughly 19 minutes of continuous unprotected exposure for Fitzpatrick skin type I, and roughly 95 minutes for type VI. The full type I–VI table is below, with the arithmetic and the sources.

Computed from a dose rate of 6.3 standard erythema doses per hour at UV index 7. Reference values, not measurements of any individual.
Fitzpatrick skin type	Reference dose to first erythema (SED)	Minutes to that dose at UV 7	0.6 × that figure (min)
Type Ialways burns, never tans	2	19	11
Type IIusually burns, tans minimally	2.5	24	14
Type IIIsometimes mild burn, tans uniformly	3.5	33	20
Type IVburns minimally, always tans well	4.5	43	26
Type Vvery rarely burns, tans easily	6	57	34
Type VIdeeply pigmented, never burns	10	95	57

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 7 question. The app answers yours.

Real days do not sit at 7 — 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 7 means

Seven is the top of WHO’s High band and, for much of the temperate world, close to the highest reading a normal clear summer day produces. One more point moves the reading into Very high.

Seven is also where the difference between skin types stops being academic. Because the reference minimal erythema dose spans a factor of five from Fitzpatrick type I to type VI, the modelled thresholds in the table below span the same factor of five at every index value — the index sets the rate, the phototype sets the target.

Where and when UV 7 actually occurs

Seven is the ceiling a temperate summer usually reaches and roughly the floor of a subtropical one. Readings of 7 typically come from:

Clear-sky summer midday across much of the temperate mid-latitudes; for many such locations this is at or near the annual peak.
Midday through most of the warm half of the year in the subtropics.
A mid-latitude location that reads 6 at sea level, roughly 1200 metres higher up — WHO also expresses the altitude effect as about 4% per 300 metres, which needs about four such steps to lift a 6 to a 7.
Inside the four-hour window around solar noon, which WHO identifies as carrying the day’s maximum reading.

A day that peaks at 7 spends only a small part of itself there. WHO’s figure of about 60% of daily UV received between 10 a.m. and 2 p.m. describes the concentration: the peak reading is a short plateau, not the day’s average.

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

What the published guidance says at UV 7

Seven is the last value in the US EPA’s “Moderate to High” grouping, for which it publishes: “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.” The EPA’s wording changes at 8.

WHO’s guide also records that sunscreen “should never be used to prolong the duration of sun exposure”, and that shade, clothing and hats “provide the best protection” with sunscreen applied to the parts that remain exposed.

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 7, an hour of continuous exposure delivers 7 × 0.9 = 6.3 standard erythema doses. Fitzpatrick type II’s reference dose is 2.5 SED, so 2.5 ÷ 6.3 × 60 = 24 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 quickly can you burn in UV 7?: At UV index 7 the model computes a first-erythema reference dose in about 19 minutes of continuous unprotected exposure for Fitzpatrick type I skin and about 95 minutes for type VI. These are computed model outputs for a reference dose, not durations of demonstrated safety.
Is UV 7 dangerous?: The published schemes do not use that word. WHO classifies 7 as the top of the High band (6 to 7) and describes the index as “an indicator of the potential for skin damage”; the EPA publishes “Protection needed” for the whole 3-to-7 range and changes its wording only at 8.

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 →