Late June brought high readings to the coastal city and elsewhere in the country, particularly in the west, with the figure surpassing level 8 on a scale of (low) to 11+ (extreme). The UV index is an international standard and is most useful to help gauge sunburn risk.

On June 25, 2026, Estonia's highest recorded UV index was taken in Haapsalu, with a reading of 8.9. The previous record dated from 2008, when a UV index of 8.6 was measured in Tõravere, matched again in 2011 in the same location. University of Tartu atmospheric remote sensing researcher Margit Aun noted that while the Haapsalu reading was a record, the substantive difference was marginal.

"When talking about the UV index, we usually don't even mention decimal places as the order of magnitude is what really matters. But, fundamentally, it's still true that the higher the number, the more hazardous it is," she said.

Also on June 25, a UV index of 7.7 was measured in Pärnu. Aun explained that such high values require several variables to coincide.

"When bright white clouds are located near the sun, multiple dispersion occurs, amplifying the amount of radiation reaching the ground when compared with a completely cloudless sky. Because of the presence of clouds, we can actually get more radiation than if there were no clouds at all," she said. Exceptionally clean air levels and a relatively thin ozone layer may also have contributed this time around.

Haapsalu's previous highest UV index of 8.2 was recorded in July 2021. In Pärnu, the previous record was 7.6, in July last year, 2025.

Despite most of these readings coming from recent years, according to Aun, it is still too early to draw firm conclusions about longer-term trends. Changes in the long-term UV index depend primarily on what is going on in the atmosphere, since the amount of solar radiation reaching the highest points of the atmosphere tends to change only very little. Much depends on cloud cover: If the lower atmosphere is clearer and there are fewer clouds, more ultraviolet radiation reaches the ground.

"Globally, the amount of aerosols, which increase the amount of radiation reaching the Earth's surface, is decreasing. On the other hand, a recovering and thicker ozone layer blocks more ultraviolet radiation, reducing the amount that reaches the ground. So it is the combined effect of different factors that determines how much radiation actually reaches the surface," the researcher said.

Aun warned against two common UV misconceptions held by the public and which they should heed, relating to shade and ambient temperature.

"First, people think that once they move into the shade, they are completely protected from UV radiation, which is simply not the case," the atmospheric scientist said.

The second misconception is that UV radiation is linked to air temperature. People travel to more southerly climes, for example, for the hotter weather, but when summer temperatures there dip, relatively speaking, say to the 25C-mark, this can lull people into a false sense of security about radiation levels.

"Because that's similar to an Estonian summer, it doesn't seem dangerous. In reality, the amount of UV radiation is not directly related to temperature. When the sun is higher in the sky and if we're in southern countries, we get sunburned much more quickly," Aun stressed.

Basics of the UV index

The Environment Agency (Keskonnaagentuur) noted in a blog post that while Haapsalu's new reading is rare for these latitudes, the record shows that UV radiation in Estonia can still reach dangerously high levels.

At Estonia's latitude (57.3°N to 59.5°N) UV index values vary considerably throughout the year and depend primarily on the sun's elevation above the horizon. During the winter months when the sun stays low in the sky and daylight hours are short, ultraviolet radiation is very weak and the UV index generally remains below two.

UV radiation is strongest in midsummer, in June and July, when the sun reaches its apex during the day. In sunny weather, the maximum UV index is usually found to be above six at this time of year, while on some days such as those seen recently in Pärnu and Haapsalu, it exceeds eight, indicating a very high level of radiation. During the sunniest months, June and July, a high UV index may be seen for around 20 days in a month, or two thirds of the time. Then from August onward, the UV index gradually recedes as the sun sits lower in the sky, with daily peaks generally falling to around five toward the end of the month.

What is the UV index?

The UV index is a measure of the intensity of the sun's ultraviolet radiation. The higher its value, the more intense the UV radiation, and the greater the risk of damage to the skin and eyes. With higher readings, harmful effects can present more quickly.

The UV index is influenced primarily by the sun's elevation, the thickness of the atmospheric ozone layer and cloud cover, including the volume, altitude and type of cloud cover. Surface reflectivity and geographic location also play a role. As a result, the UV index at a given location varies throughout both the day and the year.

It still has its practical uses, however. The World Meteorological Organization (WMO) and the World Health Organization (WHO) both recommend using the UV index as a standardized indicator to assess the potential health impacts of ultraviolet radiation.

The UV index is divided into risk categories which can help assess the health risks posed by UV radiation and determine appropriate sun protection measures.

In general, sun protection is recommended whenever the UV index reaches three or higher. The higher the UV index, the more quickly unprotected skin can get sunburned, making appropriate protection increasingly important.

The most effective way to protect yourself from UV radiation is to limit direct exposure to the sun around midday, to seek shade whenever possible if you do have to be out and about, and to wear clothing that covers the skin. A wide-brimmed hat and UV-protective sunglasses are also useful. If spending extended periods outdoors, sunscreen with a sun protection factor (SPF) adequate to your skin type should also be used.

High UV index expected in the coming days

Forecasters are predicting fine summer weather across Estonia in the coming days. From Wednesday through Friday, a high-pressure system dominant, dispersing clouds and allowing plenty of sunshine after some overcast and rainy days lately. As a result, the UV index will range between five and six, locally reaching as high as seven today, Thursday, and on Friday.

The thin layer of cloud which did cover the sky Wednesday only slightly reduced the amount of UV radiation reaching the ground. Even under cloudier conditions, diffuse radiation reaches the surface, tanning the skin, while when the UV index is high, prolonged time outdoors can still result in sunburn. The weekend and the start of next week are forecast to be cloudier, meaning UV index values decreasing again.

The Environment Agency measures the UV index at five monitoring stations: In Roomassaare, on Saaremaa; at Harku, near Tallinn, and at Tõravere, near Tartu, as well as at the Haapsalu and Pärnu stations referenced above.

The Environment Agency's website provides UV index readings in real time here and in the ILM+ app.

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