Fire can refer to both the technology and the natural disaster.
As a technology, it is research early on and it is shown to lead on the population growth. It will be important to keep your people warm during the harsh winters and to keep away predators.
As a natural disaster, it can be an inferno that starts by thunder or by human mistake. It can be stopped either by burning out or if you drag a rain cloud over the fire which will put it out. But be careful doing this because the area that didn't get the water can be effected over time.