BW has it right, mittens will be warmer, your fingers can use the buddy system. That being said, I used a pair of gloves made by Kombi. They were both water and windproof and they just plain worked. No cold hands for me.
I also had a pair of thin, windproof fingerless gloves which could be used as mittens. I only used those around camp and to type in my pecking pocketmail and found that if it was cold, you will find ways to accomplish your tasks with gloves on.
Don’t just use “an extra pair of socks” as someone will inevitably and inescapably suggest. Your hands will be cold, you will look like a goof, and you can’t pick your nose.
Officer Taco