Board Thread:Naruto Discussions/@comment-25409224-20140913064011/@comment-24649454-20141014152023

From the 3rd databook:

pg 235, Fire Style: Art of the Magnificent Dragon Flame, Ninjutsu, Rank B

...This Jutsu places emphasis on power and certainty of the attack rather than the range of the attack. The flames create a rising air current that is so hot it creates thunderheads.

pg 247, Kirin, Ninjutsu, Rank S

Sasuke created this to be the ultimate lightning jutsu. He uses a Fire Style jutsu such as the Dragon Flame Technique to quickly heat the air and create a violent rising current of air. The ring current creates thunderheads which in turn create lightning, which is guidable toward a specific target. It is a relatively low-impact chakra on the user...

Source: I'm holding the book in my hand and reading it :P