…I gotta wear shades.” (Sorry if you now have that song stuck in your head for the day.)
Sunglasses seem like a natural idea when outside on sunny days and they are. But for cyclists, the sunglasses also protect our eyes from debris, rocks flung from tires and when going really fast, bugs from hitting our eyes. Riding while trying to get a bug or other debris out of your eye is very dangerous so avoid it to begin with.
Finding glasses with lenses of different shades is important. On gray, overcast days, you don’t need as much sun/UV protection but you still need the debris protection, so change to a light colored or clear lens.
Bicycling Magazine recently rated some of the top sunglasses for cyclists. While the Rudy Project glasses look and are great, they aren’t in my budget. I do have the Tifosi that I bought at Plano Cycling and love them. Even bought my wife a pair.