Hot springs,thermal springs and warm springs. What's the difference?

Springs rising with water temperatures well above ambient have a fascination borne out of curiosity, spectacle and sometimes a need to understand the origins of the groundwater and its composition. While hot springs bring to mind boiling waters, explosive emissions of steam and volcanism, many exit temperatures are far lower than the boiling point of water, yet remain elevated above the mean air temperature or those of other springs in the surrounding country. This has led to some confusion in naming these springs. When does a hot spring cease to be hot?