Although small amounts of UV radiation are beneficial to health, overexposure can lead to skin cancer. The main determinant of UVI is the sun's elevation angle. UVI values are thus greatest in the summer, especially near solar noon. At mid-latitudes, peak UVI can reach summer peak values greater than 10, but in winter, the UVI values are generally less than 1. Peak UVI values can exceed 20 in the tropics, where seasonal variations are much smaller. The highest values in the world occur in the hi