Lightning is hotter than the surface of the sun

A lightning return stroke heats its channel to about 30,000 kelvin. The Sun’s photosphere is about 5,800 kelvin.

The current in a return stroke is tens of thousands of amperes in a channel a few centimetres wide. The energy dumps into that thread faster than the air can get out of the way. Spectroscopic temperatures land near 30,000 K. The photosphere, the visible surface, sits near 5,800 K.

The solar core is millions of kelvin and is not the comparison. The channel is also gone in microseconds, expanded into a thunder shock. Hotter, here, is a brief thread, not a rival sun.