The co2 inflators do not work well, or at all in 20 degree weather. They get so cold the nozzle freezes up and it will not fill. It helps if you put it under your coat for a while first and warm it up, then fill it up right away without too much exposure to the cold. Also in the cold there is a lot less pressure in the cartridge. a lot less. If you need two carts to fill your tire in the summer it won't work if it's cold. If it's important to you, carry a pump in the winter. The cartridges will lose pressure in a year. Just get now ones every season. I like the way they work in the summer