When you see lightning split the sky during a storm, that brilliant flash is actually a channel of superheated air. The temperature inside a lightning bolt can climb to approximately 30,000 Kelvin (about 30,000°C or 54,000°F), while the sun's surface sits at a relatively cool 5,778 Kelvin. This extreme heat is generated in an incredibly short time—the entire stroke lasts only microseconds—which is why lightning is so violently bright.

The reason lightning gets so hot comes down to electrical resistance and energy density. When millions of volts of electricity jump from a cloud to the ground (or between clouds), they force their way through air, which is normally an insulator. The electrical current encounters tremendous resistance from air molecules, and all that electrical energy gets converted into heat in a very narrow channel—often just a few centimetres wide. It's similar to how a wire gets hot when too much current flows through it, except the 'wire' here is a thin column of air.

The extreme heat causes the air in the lightning channel to expand explosively fast—faster than the speed of sound. This rapid expansion creates a shock wave that we hear as thunder. The air expands so violently that it ionizes (loses electrons), turning into plasma, which is why the lightning glows so brightly. Once the stroke ends and the current stops, the channel cools almost as quickly as it heated up, but not before leaving its mark—sometimes a burn mark on a tree, or a fulgurite (a glassy tube) fused into the ground where lightning struck sand.

So while the sun maintains its 5,778 Kelvin surface temperature continuously through nuclear fusion over billions of years, a lightning bolt achieves even greater temperatures through sheer electrical violence—but only for a millionth of a second. It's a reminder that engineering and nature both exploit extremes: the sun does it with time and scale, while lightning does it with concentrated power.