fire shields effect only happens when the creatures attack, and does not affect creatures with momentum, so deflag, steal, butterfly effect, pulvy all remove the shield from your opponent, and sundial can prevent your creatures from attacking for a turn in hopes to draw one of those cards, and momentum let you bypass it altogether
your card as of right now, has the damage dealt to all but immaterial creatures no matter what (immaterial not being affected by thunderstorm in the first place), and since the damage is cumulative, unlike fire shield, getting 6 out means your opponent has to use quints, phase dragons or immortals, or creatures with at least 7 hp, just to survive 6 of them, and at least 5 hp to survive 2 turns with only 2 in play.
and you want to make it immaterial and not cumulative, which means all your opponents creatures take 1 dmg no matter what, and there is no way to stop it from happening, unlike fire shield, which needs a protect artifact to prevent it from being destroyed.
also, fire shield unupped costs 6, and 4 upgraded, your card does a better job at dealing damage than fire shield, and costs less to get out.
other things
Thundermeter - weird name, mind explaining if it means anything, or maybe you think its a different word and merely misspelled it?
The card text itself has errors, and can be changed to make more sense.
At the end of your turn if you have less HP than your opponent, your opponent's creatures each receive 1 damage.