And then there is Florida spring fed.
|Weeki Wachee Spring|
North of Tampa
Can you see the cave?
It's actually a labyrinth in the geology below through which groundwater gushes to the surface at a fairly constant rate all year round. During the summer the water is cold and during the winter it turns warm. Actually, the water temperature stays the same, it's just the seasonal change in the air temperature above that makes it seem that way.
Or is it actually boiling?
The motion of the water gushing to the surface gives that appearance, and thus comes the name of the source of each spring: the boil.