How hot can lightning get?

A thunderstorm on a hot summer afternoon might cool down the air outside, but the air around the lightning itself can get incredibly hot. Lightning is electricity, so it does not have a temperature by itself. However, as the lightning passes through the air, or strikes an unsuspecting tree, it heats the surrounding medium into a plasma state with temperatures reaching up to about 50,000 °F (27,760 °C). That is five times hotter than the surface of the Sun.

Lightning begins with a channel in the air that is ionized, its atoms stripped of electrons and thus electrically charged. The surrounding air turns into a plasma state. An initial downward or leader stroke meets with an upward stroke of electricity, of the opposite polarity as the down stroke, that comes up from the ground and joins the cloud with the ground. These upward strokes can reach electric currents of 30,000 amperes and speeds of one-third the speed of light. Temperatures in that high-energy upward stroke channel can reach about 50,000 °F. This process happens in mere milliseconds, and when the lightning rapidly heats up the air, the air expands at lightning speed, creating sound waves we hear as rumbles or claps of thunder. Given how hot lightning can get, and how much electricity flows through it, it is always advisable to stay in a safe place when lightning is nearby, and furthermore it is wise not to try to catch something so hot in a bottle.