Is Lightning Hotter Than the Surface of the Sun?

Yes — a bolt of lightning is about five times hotter than the surface of the Sun. A lightning channel heats the surrounding air to roughly 30,000 Kelvin (about 29,700°C), while the Sun's visible surface simmers at a comparatively mild 5,500–6,000 Kelvin.

How does the sky get that hot?

It starts inside a thundercloud, where ice crystals and water droplets collide and build up enormous electrical charges — the top of the cloud becomes positive, the bottom negative. When the voltage difference grows large enough, the air itself breaks down and a channel of ionised plasma rips through the sky.

For a few millionths of a second, an electric current of tens of thousands of amps surges through that narrow channel. All that energy dumped into a tiny volume of air produces extreme heat — hotter, briefly, than the surface of our star.

That's what thunder is

The violent heating makes the air expand explosively, faster than the speed of sound. That shock wave is thunder. Lightning and thunder happen at the same instant; we see one before hearing the other only because light travels so much faster than sound — about three seconds per kilometre.

Perspective check

To be fair to the Sun, its core burns at around 15 million Kelvin — far beyond anything lightning achieves. But the part of the Sun we actually see, the photosphere, loses to a summer thunderstorm. The most violent heat most of us will ever witness is not in space at all. It is right above our heads.