I keep a baseball hat in my bag for such occasions. The I wear the hat under my helmet, brim of hat keeps the rain off of my glasses. Mine are also safety glasses from home depot, but they do wrap and don't fog up. In the summer I love to ride in the rain. When it gets in the 50's I bring a rain jacket to keep my core warm. I bring a set of clothes to work, my panniers are waterproof. 12.5 mile ride, I'm going to be wet anyway. For cold weather gloves I take the liner out of my ski gloves and wear my bike glove in them. Waterproof and warm.

you could also RainX you glasses