You are so attuned to the elemental powers that you wield; be they spells, emblazoned weapons, or something else, that you can manipulate your environment to give you an edge while you summon the powers of your attacks.
If you make an attack that deals elemental damage, while you are standing within 5 feet of that element (i.e. casting a fire spell while standing on the lip of a volcano, or casting ice spells in the rain), you may add your proficiency bonus to the damage of your attack.

Additionally, when you critically hit with an elemental attack and are surrounded by the element you are summoning, you may roll an extra damage dice.