What does Ultraman mean by burning a fire to keep warm?

The expression "Ultraman burns a fire to keep warm" means that the weather is very cold now, and even Ultraman needs to burn a fire to keep warm. It describes the extremely cold weather and everyone can't stand the cold anymore. Had to go to work. In this expression, Ultraman itself does not need to burn firewood, and since it is setting fire, it cannot feel the cold. Therefore, even Ultraman is keeping warm, which can only mean that the weather is in a very cold state.