Yes! UV rays can quite easily penetrate clouds and if you are in a part of the world where the sun is particularly strong, or you are having a heatwave, the UV rays coming from the sun will be a lot more concentrated. Just because the sun is behind the clouds does not mean you are safe from sun damage, and being in a cold climate doesn’t mean you’re safe either. In Norway and Greenland, for example, the sun bouncing off of the snow is enough to cause sunburn, even though the climates are generally colder.