When it's cold out the blood vessels in your fingers get a bit smaller which restricts the blood flow to your fingers.
That then causes your fingers to get numb because there's not much blood flow.
When your hands get warmed up the blood flow increases and the numbness goes away.
During cold weather it's very normal for our fingers and even toes to stiffen up and be a bit hard to move due to the loss of blood flow.
The blood also flows slower the colder it is just like engine oil in an engine when it's cold the engine oil flows slower but when it gets warm the oil flows faster and easier.
So you should keep your hands warm by wearing warm gloves or use some hand warmers in your gloves.
There's also another condition that some people suffer from that make peoples hands and fingers numb which is called Raynaud's disese.
The Raynaud's disease causes fingers and toes to get numb and cold in response to cold temperatures and even stress.