The Talmud states it perfectly: “Thunder was created only in order to straighten the crookedness of the heart” (Brachot 59a). As few other phenomena can do, thunder wakes us up and reminds us we have an all-powerful God. Of course, there are always scientific explanations for such natural events. But why did God create them in the first place? To give us that occasional wake-up call.

Many years ago, I was about to do something of questionable legality in Jewish law. Just then the loudest peal of thunder you ever heard struck – and I realized God had me in mind.

Apart from the philosophical perspective, the Sages instituted different blessings to be said both on thunder and lightning. On thunder we say:

“Blessed are You, God, King of the universe, for His strength and power fill the world.”

And on lightning:

“Blessed are You, God, King of the universe, who makes the works of creation.”

Note that we recite a stronger blessing on thunder than on lightning, in that thunder is a much stronger manifestation of God’s might (Mishnah Berurah 227:5).

A few additional rules:

(a) You must begin reciting the blessing immediately (within 1-2 seconds) upon hearing the thunder or seeing the lightning (Shulchan Aruch 227:3). If you weren’t able to start the blessing that soon, you should wait until you observe the next clap of thunder or flash of lightning.

(b) You don’t have to see the bolt of lightning itself to recite a blessing. It’s sufficient to see the sky light up.

(c) We only recite these blessings a maximum of one time a day. The exception is if the sky clears entirely after a storm, and afterwards a new storm appears (Shulchan Aruch 227:2, Mishnah Berurah 8).

(d) We don’t recite a blessing on "heat lightning" – where the sky lights up without thunder (Mishnah Berurah 3).