As the United Kingdom faces forecasted extreme heat, ultraviolet radiation levels are anticipated to reach elevated levels across many regions. Health authorities are using the opportunity to reinforce guidance on sun exposure and protective measures.
Ultraviolet radiation originates from the Sun and penetrates Earth’s atmosphere. While some UV exposure is beneficial for human health—enabling skin to produce vitamin D, which supports bone function, blood cell production, and immune system activity—excessive exposure carries significant risks. Overexposure to UV can damage DNA in skin cells, leading to skin cancer development. The radiation also contributes substantially to skin aging, causing wrinkles and skin laxity, and has been associated with eye conditions including cataracts. According to Prof Dorothy Bennett from St George’s, University of London, melanoma, the most dangerous form of skin cancer, is now the fifth most common cancer in the UK.
UV radiation intensity varies throughout the day, with the highest levels occurring during a four-hour window around solar noon, typically from late morning to early afternoon. The UV Index measures ultraviolet radiation intensity on a scale beginning at zero and potentially exceeding 10, with higher values indicating greater potential for skin and eye damage and shorter timeframes for harm to occur. In the UK, summer UV levels typically range from 5-6, with maximums of 8 only under exceptional conditions. By contrast, countries near the equator experience significantly higher levels year-round, with Nairobi, Kenya recording levels above 10 throughout the year and Majorca, Spain typically reaching 9 during June and July.
Health authorities recommend applying sunscreen with an SPF factor of 30 or above offering at least 4-star UVA protection to all exposed skin approximately 30 minutes before sun exposure, with reapplication every two hours or after swimming or perspiring heavily. The NHS suggests adults apply approximately six to eight teaspoons when covering the entire body. Additional protective measures include wearing appropriate clothing and sunglasses, and seeking shade between 11:00 and 15:00 from March to October in the UK. Children require additional protection due to heightened sensitivity to UV radiation. Weather conditions do not reduce UV risk, as radiation penetrates clouds and skin can burn equally quickly at temperatures of 20 degrees Celsius or 30 degrees Celsius. Eye damage and immune system effects from excessive UV exposure affect individuals of all skin tones.