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What is the UVI? -

The ultraviolet index, or UVI, is an international standard measurement of the strength of the sunburn-producing ultraviolet (UV) radiation at a particular place and time.

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How is UVI measured? -

The UVI is indicated by an index number, color scheme, and exposure category: 1-2 Low; 3-4-5 Moderate; 6-7 High; 8-9-10 Very High; 11+ Extreme.

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Bolivia -

Throughout the Altiplano region of Peru, Bolivia, and Chile, UVI values regularly exceed 20, according to ResearchGate.

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Peru -

Confirming this research is the UVI of 25 centered on Cuzco, in southern Peru, recorded by the National Institute of Water and Atmospheric Research in New Zealand (NIWA).

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Chile -

The bulk of the Altiplano lies in Bolivia, but its northern parts lie in Peru, and its southwestern fringes lie in Chile. The Altiplano's elevated topography is a contributory factor in the extreme UVI found in this part of the world. But this region is not the only travel hotspot that could be damaging to your health.

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Sri Lanka -

Peak UV occurs within the tropics (high sun, low ozone), at a high altitude site, and in the Southern Hemisphere. People traveling to countries that meet this criteria need to cream up well. Its location, for example, means Sri Lanka regularly records UVI of 11+ (extreme).

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Thailand -

Thailand is another dangerous holiday destination in terms of UV radiation. Mid-summer UVI levels here can also reach 11+.

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Vietnam -

Close neighbor Vietnam also records UVI levels of 11+, to make it a nation also known for high ultraviolet radiation.

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Singapore -

In fact, Southeast Asia in general is a region where care needs to be taken when venturing out in the sun. UVI in Singapore, for example, often peaks in the extreme at 11.

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Hong Kong -

Hong Kong in mid-summer can hit a UVI of 10, which is very high. And the humidity can be oppressive.

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Australia -

In summer, most of Australia has an average clear-sky maximum UVI forecast in the extreme range (11+).

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New Zealand -

UVI levels in New Zealand have been known to hit 12 and can even reach 13 in the northern reaches of North Island, according to NIWA.

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Brazil -

Across the other side of the world but still in the Southern Hemisphere, Brazil's UVI averages 10, which is still very high.

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Mexico -

Countries in Central America fall within the Northern Hemisphere, and while in this half of the world UVI tends to be lower, places like Mexico can still top out at an extreme 11 in high season.

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Panama -

Likewise, Panama has been known to peak at 11, its hot and humid tropical climate conducive to high UV.

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Cuba -

Caribbean nations also share a tropical climate with seasonal humidity and long, hot dry months. In Cuba, UVI levels can nudge up to an extreme 11.

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Barbados -

Barbados, a favorite winter sun vacation destination, experiences year-round heat and humidity. Expect an average UVI of 11.

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Jamaica -

Sunshine in Jamaica peaks through February to April. It's hot and dry, with an average 10 on the UVI.

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Kenya -

Over in Africa, UVI levels are generally high, depending on the season. In Kenya, however, a country that straddles the equator, levels are extreme, reaching 11 or more.

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Nigeria -

And even though it lies entirely in the Northern Hemisphere, temperatures in Nigeria can be equally stifling, helping to bump up the UVI to at least 11.

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USA -

Ultraviolet index levels in the Unites States largely depend on the state. Hawaii, for example, averages a summer UVI of 11 to 12, which is extreme. In fact, the United States Environmental Protection Agency (EPA) notes that at high-altitude locations, such as the Mauna Loa Observatory, the UVI can exceed 20!

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USA -

It's no surprise that Florida often records UVI levels of between 10 and 11.

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USA -

And you'd expect states in the Southwestern region of the US to boil under mid-summer heat; places like Arizona, where the average UVI is a very high 10.

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USA -

And Los Angeles in California has been known to record a dangerous 10 on the UVI, its citizens sometimes unaware of the strength of the ultraviolet rays bombarding them.

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Japan -

Back in the Far East but staying in the Northern Hemisphere, Japan is known for its seasonal climate. Eastern and Western Japan especially experience very hot and humid summers, where the UVI can easily climb to 10, notes Germany's Federal Office for Radiation Protection, or Bundesamt für Strahlenschutz (BFS).

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Dubai -

The United Arab Emirates, meanwhile, averages a UVI of 9, which is still very high.

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India -

Across India, UVI levels tend to be dangerously high, according to the season. To give you an idea, UVI in Chennai can peak at 15, while in Mumbai a level of 16 is not uncommon. Both Kolkata and Delhi record similar levels.

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Greece -

And what about Europe? Well, the BFS recorded a very high 10 in Greece recently, during the sweltering heatwave in 2023. Generally, however, the mid-summer UVI across the continent averages 6, which is still high, so precautions should always be taken.

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Antarctic Plateau -

An here's a surprise: in one of the coldest places on the planet, peak ultraviolet values on the edge of the Antarctic Plateau have in the past reached a maximum level of 8, corresponding to the typical average summer value for midlatitude sites, according to HAL.

Sources: (WHO) (ResearchGate) (NIWA) (GHP News) (EPA) (BFS) (World Weather Attribution) (HAL) (HealthMatch) 

See also: What are the dangers of UV radiation? 

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