The most common cancer risk is skin cancer. If you’ll be in the sun for an hour or more, be sure to apply sunscreen with both UVA and UVB protection. Sunscreen takes time to become active. Apply about 20 minutes before you go outside.
About SPF numbers: SPF 30 (the recommended rating) means it would take about 30 times longer for damage to occur than if you weren’t wearing sunscreen. But that’s true only if you reapply every couple of hours. Use sun protection when driving. It’s no coincidence that most US skin cancers develop on the left side of our bodies and faces.