Here's why:

* Nuclear Fusion: Stars produce energy through nuclear fusion in their core, where hydrogen atoms fuse to form helium. This process releases immense heat and light.

* Temperature and Color: The temperature of a star determines its color. Hotter stars emit more blue and white light, while cooler stars emit more red and orange light. Since most stars are white or blue, it indicates they are quite hot.

* Red Dwarfs: While most stars are hot, there are also many red dwarf stars, which are relatively cool. However, they are so small and faint that they are difficult to see with the naked eye.

So, while there are some cooler stars out there, the vast majority of stars we see in the night sky are incredibly hot.