Is UV 5 considered high?

Not by WHO’s published categories — 5 is the top of the Moderate band (3 to 5), and the High band begins at 6. It is the highest reading inside Moderate, so it sits one point below the category change.

WHO category: Moderate (3 to 5)

How long to burn in UV 5?

At UV index 5, the erythemal-dose model computes a first-perceptible-reddening reference dose after roughly 27 minutes of continuous unprotected exposure for Fitzpatrick skin type I, and roughly 2 hours 13 minutes for type VI. The full type I–VI table is below, with the arithmetic and the sources.

Computed from a dose rate of 4.5 standard erythema doses per hour at UV index 5. Reference values, not measurements of any individual.
Fitzpatrick skin type	Reference dose to first erythema (SED)	Minutes to that dose at UV 5	0.6 × that figure (min)
Type Ialways burns, never tans	2	27	16
Type IIusually burns, tans minimally	2.5	33	20
Type IIIsometimes mild burn, tans uniformly	3.5	47	28
Type IVburns minimally, always tans well	4.5	60	36
Type Vvery rarely burns, tans easily	6	80	48
Type VIdeeply pigmented, never burns	10	133	80

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 5 question. The app answers yours.

Real days do not sit at 5 — 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 5 means

Five is the top of Moderate. One more point and the reading crosses into WHO’s High band, which is why 5 is often the highest number a temperate spring or autumn day produces and the number a summer day passes on its way to something larger.

The dose rate at 5 is 5/3 that of UV 3, so every modelled threshold below is 60% of the corresponding UV 3 figure. The proportionality is not an approximation: WHO defines the index as 40 m²/W multiplied by the erythemally weighted irradiance, so doubling the index doubles the dose rate exactly.

Where and when UV 5 actually occurs

Five is about as high as a moderate sun elevation gets at sea level, so it usually means either a shoulder season or a shoulder hour. Readings of 5 typically come from:

Clear-sky midday at mid-latitudes in late spring and early autumn.
Roughly an hour and a half to two hours either side of solar noon in mid-latitude summer.
Midsummer midday well into the higher latitudes.
Midday in the subtropics through winter, where the sun stays high enough year round that the index rarely drops into the low single digits.

In mid-latitude summer, 5 marks roughly the edges of the four-hour window around solar noon that WHO identifies as carrying the day’s maximum. Inside that window the reading is higher; outside it, lower.

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

What the published guidance says at UV 5

The US EPA groups 5 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.”

The EPA also publishes a shadow rule as a way of reading intensity without an instrument: a shadow shorter than you indicates stronger UV, a longer shadow weaker UV.

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 5, an hour of continuous exposure delivers 5 × 0.9 = 4.5 standard erythema doses. Fitzpatrick type II’s reference dose is 2.5 SED, so 2.5 ÷ 4.5 × 60 = 33 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 5?: At UV index 5 the model computes a first-erythema reference dose in about 27 minutes of continuous unprotected exposure for Fitzpatrick type I skin and about 133 minutes for type VI. These are computed model outputs for a reference dose, not durations of demonstrated safety.
Is UV 5 considered high?: Not by WHO’s published categories — 5 is the top of the Moderate band (3 to 5), and the High band begins at 6. It is the highest reading inside Moderate, so it sits one point below the category change.

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 →