Wildfire Elemental — ruling 1

Combat damage is the damage that's dealt automatically by attacking and blocking creatures. Any other damage is noncombat damage, even if it's dealt during a combat phase by an attacking or blocking creature.

Wildfire Elemental — ruling 2

The last ability of Wildfire Elemental triggers once for each event in which an opponent is dealt noncombat damage, regardless of how much damage that player is dealt.

Wildfire Elemental — ruling 3

Wildfire Elemental's triggered ability affects only creatures you control at the time it resolves. Creatures you begin to control later in the turn won't get +1/+0.

Wildfire Elemental — ruling 4

In a multiplayer game, if a source deals damage to multiple opponents at the same time, the last ability of Wildfire Elemental will trigger that many times.

Wildfire Elemental : règles, fonctionnement et interactions (MTG)

Wildfire Elemental is one of those cards players keep asking about. Here is, in plain words, what its official text says, the rulings published by Wizards of the Coast, and the combos players actually run.

Official card text

Whenever an opponent is dealt noncombat damage, creatures you control get +1/+0 until end of turn.

How it works : Wildfire Elemental

Original English text — Wizards of the Coast / Scryfall

#1July 12, 2019· Wizards of the Coast
Combat damage is the damage that's dealt automatically by attacking and blocking creatures. Any other damage is noncombat damage, even if it's dealt during a combat phase by an attacking or blocking creature.
No other card is named in this ruling.
#2July 12, 2019· Wizards of the Coast
The last ability of Wildfire Elemental triggers once for each event in which an opponent is dealt noncombat damage, regardless of how much damage that player is dealt.
No other card is named in this ruling.
#3July 12, 2019· Wizards of the Coast
Wildfire Elemental's triggered ability affects only creatures you control at the time it resolves. Creatures you begin to control later in the turn won't get +1/+0.
No other card is named in this ruling.
#4July 12, 2019· Wizards of the Coast
In a multiplayer game, if a source deals damage to multiple opponents at the same time, the last ability of Wildfire Elemental will trigger that many times.
No other card is named in this ruling.