[RPG] Is thunder damage associated with lightning dragons

damage-typesdnd-5esorcererspells

Draconic Bloodline sorcerers gain Elemental Affinity at level 6. I was wondering if the sorcerer's bloodline was that of a lightning dragon do they gain the EA bonus to thunder damage spells as well as lightning damage spells?

Best Answer

No

Draconic Ancestry explicitly tells you the damage type "associated with each dragon type [which] is used by features you gain later." (PHB p.102, emphasis mine)

So you've gotten lightning damage type from your ancestry. No mention of thunder. When you gain Elemental Affinity, lightning is the damage type.