Does a hotter day mean I need a higher SPF?

What should decide my SPF?

SPF measures protection against UVB radiation, not temperature, so the number on the bottle is not an oven setting. A higher SPF gives more UVB protection. For a long walk, outdoor sport or a working day outside, choose SPF 50 or higher even if the air feels cool. UV damage depends on both the intensity of the rays and the length of exposure. A higher number is not permission to stay outside longer: sunscreen cannot completely block UV radiation.345

Can I get sunburned when it is cold outside?

Yes. UV rays reach your skin on cool and cloudy days, and sunburn is caused by UV exposure. Snow, water, sand and concrete reflect UV rays, adding to your exposure. That makes sun protection relevant to skiing as well as beach days. Check the local UV index rather than treating cold air or cloud cover as a reason to skip protection.346

How do I use the UV index to plan sun protection?

Check your location's UV index in a weather app or on a weather website before planning outdoor time. The higher the index, the greater the potential for skin and eye damage, and the less time harm takes. UV forecasts account for clouds and other local conditions. The reported daily value usually represents the maximum around solar noon, rather than an identical level from morning to evening.136

Use 3 as the point to put sun protection measures in place, not as a formula for calculating SPF. At higher levels, reduce exposure as well as using sunscreen. Early morning and late afternoon generally have lower UV levels than midday. Shade helps, but scattered and reflected UV still reaches you under trees, umbrellas and canopies.34

How should I apply sunscreen on a hot day?

Look for broad spectrum protection against both UVA and UVB, which earns its space on the label more than another adjective about sunshine. Choose water resistant sunscreen if you expect to sweat or swim. Heat also matters to storage: exposure to high temperatures shortens sunscreen's shelf life, so check the expiry date.247

1. 1Apply sunscreen generously and evenly 20 to 30 minutes before going outside.
2. 2Cover all exposed skin, including your face, neck, ears and hands. For an adult's entire body, allow around 6 to 8 teaspoons; applying too little reduces protection.
3. 3Reapply every two hours while outdoors. Reapply after swimming, sweating or towel drying, including when the sunscreen is water resistant.
4. 4Use clothing, a wide brimmed hat and UV protective sunglasses alongside sunscreen, and take shade breaks.

Take extra care if you burn easily, have many moles or have a family history of skin cancer. If you get sunburned, stay out of the sun until the redness has gone. Seek medical help if you feel unwell or your skin swells badly or blisters.7