A bolt of lightning can heat the air around it to temperatures five times hotter than the surface of the Sun.
Why it is true
During an electrical discharge, the lightning channel rapidly reaches about thirty thousand degrees Celsius, causing the air to expand explosively and create the sound of thunder.
Source: NOAA
Would you rather be asked first?
This is the reading side of the site, so the answer is in the sentence above — that is the whole point of it. Test yourself works the other way round: the question comes on its own, and the fact and the explanation only appear once you have answered.