If you've been following the advice I've given for years to apply SPF 30 or more every day, you should be in good shape. When spending extended time outdoors, reapply as needed while working up a sweat or when spending time in the water.
If your job or summer activities like walking, biking, or gardening, keep you in the sun for extended periods, consider clothing rated for its UPF (UV Protection Factor).
A white, dry cotton shirt provides an UPF of about 8. UPF-rated clothing up to 50 is widely available.
A Few Other Things to Know About the Sun's UV Rays
- Reflected UV radiation is just as damaging as direct UV radiation.
- Sand/concrete reflects 25% of UV radiation.
- Water reflects up to 100% of UV radiation.
- Snow reflects 85% of UV radiation.