Since UVA rays penetrate glass and clouds, use sunscreen even when it's cloudy or you're indoors but in rooms with lots of Windows.

The sun can reach you on cloudy, rainy, or snowy days as well. Plus, Sadick adds, "skin-damaging UV rays can penetrate through glass, so you need to apply sun protection even indoors."

If you focus the sun's rays on dry wood with a burning-glass, it will start burning.