Lightning Cloud — ruling 1

Triggers when the spell is cast.

Lightning Cloud — ruling 2

You pick the target when putting the triggered ability on the stack, but you don’t choose whether or not to pay {R} until the triggered ability resolves.

Lightning Cloud : règles, fonctionnement et interactions (MTG)

Lightning Cloud 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 a player casts a red spell, you may pay . If you do, this enchantment deals 1 damage to any target.

How it works : Lightning Cloud

Original English text — Wizards of the Coast / Scryfall

#1October 4, 2004· Wizards of the Coast
Triggers when the spell is cast.
No other card is named in this ruling.
#2October 4, 2004· Wizards of the Coast
You pick the target when putting the triggered ability on the stack, but you don’t choose whether or not to pay until the triggered ability resolves.
No other card is named in this ruling.