Lightning reaches temperatures that defy the imagination and far exceed solar heat.
During the brief moment of electrical discharge, a lightning bolt can reach temperatures of approximately 30,000 degrees Celsius (54,000°F), while the surface of the Sun records "only" 5,500°C (10,000°F).
This extreme temperature is generated when millions of volts of electricity pass through the air in fractions of a second. The electrical discharge ionizes the air molecules, creating a superheated plasma channel that produces the characteristic bright light of lightning.
The instantaneous heat causes the air to violently expand, generating the shock waves we perceive as thunder. Although the temperature is extraordinary, the duration is so brief (microseconds) that the lightning cannot transfer enough energy to cause the same damage as prolonged exposure to lower temperatures.
Source: Atmospheric Physics Quarterly
