When a lightning bolt strikes, it superheats the surrounding air into a plasma channel, reaching temperatures of around 50,000°F (27,760°C). This figure is cited by authoritative sources including Weather.gov (NOAA) and Britannica, making it one of the most extreme temperatures found in nature on Earth.
For context, the Sun's photosphere — what we see as its visible surface — sits at roughly 10,000°F (5,500°C). Lightning's plasma channel is therefore approximately five times hotter than the solar surface. NASA confirms the Sun's surface temperature at ~10,000°F, while its core reaches a far greater 27 million°F, which lightning cannot approach.
It's worth noting that lightning's extreme temperature is a fleeting, localized event lasting only microseconds. The intense heat causes the surrounding air to expand explosively, which is what produces the crack of thunder.