UK — UV levels are forecast to be high in many areas of the United Kingdom due to anticipated extreme heat. Ultraviolet (UV) radiation is emitted by the Sun and penetrates the Earth's atmosphere, and excessive exposure can damage DNA in skin cells, leading to skin cancer.

Exposure to UV radiation allows human skin to produce vitamin D, which supports bone, blood cell, and immune system function. However, UV exposure also contributes to skin aging and is linked to eye problems such as cataracts. Professor Dorothy Bennett stated, "Every exposure to UV, especially every sunburn, increases our risk of skin cancer." She added, "Melanoma, the most dangerous skin cancer, is now the fifth commonest cancer in the UK."

The UV Index (UVI) measures ultraviolet radiation globally, with values starting at zero and increasing higher than 10. Higher UVI numbers indicate a greater potential for damage to skin and eyes and a shorter time for harm to occur. In the UK, the UV index typically ranges from 5-6 during the summer, reaching a maximum of 8 only in exceptional circumstances. The World Health Organization (WHO) advises sun protection in the UK when UV levels are medium (3-5) or high (6-7), and extra protection for very high (8-10) or extremely high (11+) levels.

The National Health Service (NHS) recommends using sunscreen with an SPF factor of 30 or above, alongside at least 4-star UVA protection. Sunscreen should be applied to all exposed skin, including the face, neck, ears, and scalp if hair is thinning or absent, ideally 30 minutes before sun exposure. The NHS advises adults to apply six to eight teaspoons of sunscreen for full body coverage and to reapply it every two hours, or sooner if sweating heavily, after water exposure, or after towel drying.

The NHS also suggests covering up with suitable clothing and wearing sunglasses. Spending time in the shade when the sun is strongest, between 11:00 and 15:00 from March to October in the UK, is also recommended. The NHS states there is no safe or healthy way to get a tan. Dr. Bav Shergill from the British Association of Dermatologists recommends using self-tanning products instead of tanning. He explained, "When you tan, ultraviolet light stimulates your skin cells to produce pigment to try and protect the DNA of skin cells - but that protection is minimal - the equivalent of SP4." Shergill added, "That is not much protection at all - so you can still burn very early."

Weather presenter Helen Willetts noted, "Your skin can burn just as quickly whether it's 30C or 20C." She also advised, "Don't be caught out on cloudy days." Willetts stated, "UV will still penetrate thin clouds - so even if you don't think it's that sunny, you can still burn." Dr. Shergill indicated that people with brown skin are also at risk from UV radiation. He said, "The skin may look darker, but it doesn't always behave that way from a protection point of view – because there are more genes at play than we think about." He cited examples, stating, "I have, for example, seen South Asian people with skin cancer and I have seen people with dual-heritage get skin cancer."