TL;DR
NHS and Met Office guidance recommends limiting direct sun exposure between 11am and 3pm, particularly when UV levels reach 6 or above. The two-hour rule guides reapplication of sunscreen and shade breaks during periods of high UV.
NHS and Met Office guidance on sun exposure recommends limiting direct sun between 11am and 3pm, particularly when UV levels reach 6 or above on the index. The two-hour rule is the practical reapplication guideline that follows the British Association of Dermatologists advice on sunscreen and shade.
Where the two-hour rule comes from
The two-hour rule covers the reapplication interval for SPF sunscreen during sun exposure. The British Association of Dermatologists recommends reapplying sunscreen at least every two hours, plus after swimming or sweating heavily.
Direct exposure between 11am and 3pm, when UV is highest, should be limited where possible. The Met Office UV index forecast indicates how strong UV will be on a given day and underpins the guidance.
How the UV index works
The UV index runs from 0 to 11-plus. Levels 1 to 2 are low, 3 to 5 moderate, 6 to 7 high, 8 to 10 very high and 11 or above extreme. In the UK, levels of 6 or 7 are typical during summer heatwaves at midday.
UV is highest when the sun is directly overhead, typically between 11am and 3pm in the UK during summer. Cloud cover reduces UV but does not eliminate it; reflective surfaces such as water and snow can increase exposure.
Sunscreen and shade in practice
NHS guidance recommends an SPF of at least 30 with four or five star UVA protection. The British Association of Dermatologists notes that most people apply less sunscreen than the test conditions assume, so a generous application is needed for the labelled SPF to be effective.
Hats, loose clothing, sunglasses with UV protection and shade complement sunscreen. Babies under six months should be kept out of direct sun entirely.
Vitamin D considerations
Short periods of unprotected exposure produce vitamin D, which supports bone health and immune function. NHS guidance suggests 10 to 15 minutes of exposure to bare skin around midday between April and September is enough for most adults.
Public Health England recommends a 10 microgram vitamin D supplement during autumn and winter for the general population, and year-round for people with little exposure such as those who cover their skin for cultural reasons or who spend most time indoors.
Skin cancer and when to see a GP
Skin cancer is the most common cancer in the UK and most cases are linked to UV exposure. The NHS ABCDE rule for moles flags Asymmetry, Border irregularity, Colour variation, Diameter over 6mm and Evolving changes as warning signs.
Any new mole or change to an existing mole should be discussed with a GP, who can refer to a dermatology service if needed. Cancer Research UK publishes detailed self-check guidance.
Key facts
- Reapply sunscreen at least every two hours.
- UV index 6 to 7 is typical at UK midday in summer.
- Use SPF 30 or higher with four or five star UVA protection.
- Babies under six months should be kept out of direct sun.
- 10 microgram daily vitamin D supplement recommended in winter.
FAQ
What is the two-hour rule for sun exposure?
Reapply sunscreen at least every two hours during direct sun exposure, plus after swimming or sweating heavily. The British Association of Dermatologists publishes the recommendation alongside Met Office UV forecasts.
How strong is UV in the UK?
The UV index reaches 6 to 7 at midday during summer heatwaves, which is classed as high. Cloud cover reduces UV but does not eliminate it, and reflective surfaces such as water can increase exposure.
What SPF should I use?
NHS guidance recommends SPF 30 or higher with four or five star UVA protection. Generous application matters because most people apply less than the test conditions assume.
Should I worry about a mole that has changed?
Any new mole or change to an existing mole, particularly involving asymmetry, irregular borders, colour variation, diameter over 6mm or evolving features, should be discussed with a GP.
