How to Protect Yourself from UV

Timing your time outside

The cheapest sun protection is choosing when you go. The WHO advises limiting time in the midday sun and seeking shade (WHO). The Skin Cancer Foundation names 10 AM to 4 PM as the peak hours of sun intensity, and the NHS says that in the UK the sun is strongest between 11am and 3pm from March to October.

Check the UV index too. The NHS says to protect your skin when it is 3 or higher (NHS). If your free time covers both midday and late afternoon, the later hours will often carry a lower UV number. UV GO compares the UV index hour by hour alongside rain, heat, cold and wind, and picks the lowest average score within your free time.

Sunscreen: SPF, amount, reapplying

The WHO puts sunscreen in its place: use broad-spectrum sunscreen on the skin that clothing cannot cover, and do not use sunscreen to extend the time you spend in the sun (WHO). Cancer Council Australia and the NHS say the same.

The health bodies agree on the basics and differ on the details:

• SPF. The NHS and the American Academy of Dermatology (AAD) recommend at least SPF 30. The Skin Cancer Foundation recommends SPF 30 or higher every day, and SPF 50 or higher with a water-resistant formula for extended outdoor activity. Cancer Council Australia recommends SPF 50 or 50+, broad-spectrum and water resistant.
• Broad spectrum. The label should say it covers UVA and UVB. The NHS asks for at least 4-star UVA protection.
• Amount. The AAD says adults need about 1 ounce, roughly a shot glass, for the whole body, and at least 1 teaspoon for the face. The NHS gives 6 to 8 teaspoons for a whole adult body, and Cancer Council Australia gives 35 mL, about seven teaspoons.
• Before you go. The AAD says it takes about 15 minutes for skin to absorb sunscreen and protect you. Cancer Council Australia says to apply it 20 minutes before going out.
• Reapply. Every two hours, and straight after swimming or sweating, according to the AAD, the NHS, the Skin Cancer Foundation and Cancer Council Australia. The NHS adds towel drying, and Cancer Council Australia says to reapply at least every two hours regardless of water resistance.

Details from: AAD, NHS, Cancer Council Australia and the Skin Cancer Foundation.

The numbers differ a little because the bodies write for different countries and labelling rules. The practical takeaway is the overlap: at least SPF 30, a generous amount, a few minutes before you leave, and again every two hours.

The AAD lists the spots people miss: neck, ears, tops of the feet and legs. It suggests help or a spray for your back, sunscreen on the scalp if your hair is thinning (or a wide-brimmed hat), and lip balm with at least SPF 30.

Clothing and hats

Clothing is the one layer you do not have to reapply. The WHO says shade and clothing are preferred over sunscreen, and Cancer Council Australia’s first step is to wear sun-protective clothing that covers as much skin as possible.

The NHS suggests a long-sleeved top and close-weave trousers or long skirts. The Skin Cancer Foundation explains that UPF stands for ultraviolet protection factor, so a shirt labelled UPF 50 lets through 1/50th of UV radiation (Skin Cancer Foundation).

For hats, the WHO recommends a broad-brimmed hat that covers the eyes, face, ears and neck. The Skin Cancer Foundation says a brim of three inches or more that goes all the way around is best, and Cancer Council Australia names broad-brim and legionnaire styles.

Sunglasses

Eyes need protection as well, as the risks article explains. The WHO recommends wraparound sunglasses that give 99 to 100% UV-A and UV-B protection. The NHS adds that wraparound lenses or wide arms help, and that in the UK you should look for the CE mark and British Standard 12312-1:2013 E. In Australia, Cancer Council Australia says to choose sunglasses that meet Australian Standards.

Shade

Shade is the second-cheapest tool after timing. The Skin Cancer Foundation calls shade your refuge, especially between 10 AM and 4 PM. The WHO says shade and clothing are preferred over sunscreen.

At the high end of the scale, the US EPA gives a quick field test for a UV index of 8 and above: if your shadow is shorter than you, seek shade (US EPA). You can check it in a second, no app needed.

Putting it together: what to take

The what-to-take list in UV GO follows the same ideas, using available values across the forecast hours of your best window. Its current thresholds are also listed in How it works:

• Sunscreen appears when the highest rounded UV in your window is 3 or above, in line with the WHO and NHS threshold above.
• Hat and sunglasses appear at UV 6 or above.
• Rain jacket appears when the chance of rain reaches 30%.
• Water appears for the Active activity, or when it feels like 25°C or more.
• Warm layer appears when it feels like less than 5°C.

When none of these rules trigger with the available data, the list says “No extra items suggested.” Missing forecast values cannot trigger an item. At UV below 3 you can still choose to protect your skin, especially if you burn easily. That is your call.

UV GO gives general guidance, not a guarantee. If you have a skin condition or are protecting a baby, ask a healthcare professional. The NHS, for example, advises keeping babies under 6 months out of direct sunlight.