Handwarmers
Keeping your hands warm
These chemical handwarmers are amazing and last for at least 12 hours. Each pack contains two so you can stick one in each glove.
When you go to bed I recommend taking them out of your gloves and putting them in your socks.
They last basically forever in their packets, so it’s efficient to buy a bunch and use them when you need them. That link is the best value I could find for 10.
How to use
Just rip open the pack they come in, you’ll find a couple of paper sachets, shake these up and put them in your gloves/pockets. They react with the oxygen in air. Over about 20 minutes they’ll start to get warm.
You need to keep them in a glove or a pocket or they can react too fast and get too warm.
Disadvantages
They’re one use only.
They’re no good when they get wet.
Alternate use
Some people tape a couple in the small of their back, each side of the spine. Apparently that works great but I’ve never done that myself.