How worried about UV should we be in winter?

Most people want to ease up on sun protection during winter as the sun feels weaker and they assume they are less likely to burn.  Sadly only one of the two UV perpetrators, UVB, is actually reduced by clouds.  And while these UVB rays are the culprit behind sunburn, the other type of UV rays, UVA, are very much present year round- and it’s imperative to avoid them.