Even if the entire Death Star vaporized in Endor's atmosphere, every living thing on that planet would be flash fried. As something burns up (Vaporizes,) it imparts it's thermal energy into the medium that surrounds it.
Science Lab (Don't do this at home.)
According to the Death Star Technical Handbook published by West End Games, the Death Star has a diameter of 120 kilometers.
Let's assume that the DS has uniform density of 1kg/cubic meter. (And since it was made of plasticrete and ceramasteel, that's being VERY generous).
Mass = Volume * Density.
Mass = (4/3) * pi * (60,000 meters)^2 *1
Mass = Approximately 15 billion kg.
Calorimetry of Steel
Heat of vaporization of Carbon 355.8 kJ/kg
Heat of Vaporization of Iron 349.6 kJ/kg
Carbon and Iron make up steel so average is 353 kJ/kg
353*15,000,000,000 = 5,295,000,000,000,000 Joules of energy pumped into Endor's atmosphere, which cooks to a plasma, while the oceans boil, vaporize, and plasmate too.
There you have it, proven by amateur Shlock science. Crispy Ewoks! Q.E.D.