Where's the fire?

Spawns are determined by biome. You, like me, are probably in an area where fire is rare. They do rarely spawn here though. Your best chance is from eggs for out of biome mons however.

I see Growlithes and Vulpix quite often but water types are rare for me.

Before I never seen a single fire mon in my biome. Since gen2 I've been encountering a lot of Vulpix and occasionally a growlith.

Consider traveling to desert biome or try to continue hatching eggs. Not sure which fire type toy are looking for?

If you're in an area where fire types are rare, you can still find them at nests. Parks are often nests, and the type of nests they are rotates every two weeks.

I live on a volcano. They are rare here too...