And the thunder exalts [Allāh] with praise of Him - and the angels [as well] from fear of Him - and He sends thunderbolts and strikes therewith whom He wills while they dispute about Allāh; and He is severe in assault.
Clouds, Thunder and Lightning are Signs of Allah's Power
Allah states that He has full power over Al-Barq (lightning), which is the bright light that originates from within clouds. Ibn Jarir recorded that Ibn `Abbas once wrote to Abu Al-Jald asking about the meaning of Al-Barq, and he said that it is water. Qatadah commented on Allah's statement,
خَوْفًا وَطَمَعًا
(as a fear and as a hope.) "Fear for travelers, for they feel afraid of its harm and hardship, and hope for residents, awaiting its blessing and benefit and anticipating Allah's provisions." Allah said next,
وَيُنْشِىءُ السَّحَابَ الثِّقَالَ
(And it is He Who brings up the clouds, heavy.) meaning, He originates the clouds that are heavy and close to the ground because of being laden with rain. Mujahid said that this part of the Ayah is about clouds that are heavy with rain. Allah's statement,
In the next verse (13), it was said: وَيُسَبِّحُ الرَّعْدُ بِحَمْدِهِ وَالْمَلَائِكَةُ مِنْ خِيفَتِهِ (And the thunder proclaims His purity with His praise, and [ so do ] the angels, out of His awe). In Arabic usage, the word: الرَّعْدُ (Ar-Ra` d)refers to the sound of the clouds generated by their collision. The sense of (Tasbih: the glorification of Allah) mentioned here is that of the same Tasbih about which it has been said in another verse of the Qur’ an: وَإِن مِّن شَيْءٍ إِلَّا يُسَبِّحُ بِحَمْدِهِ وَلَـٰكِن لَّا تَفْقَهُونَ تَسْبِيحَهُمْ 'And there is nothing in the heavens and the earth which does not glorify Allah, but they do not understand their glorification' - (17:44).
And it appears in some narrations of Hadith that Ar-Ra'd is the name of the angel appointed to bring rains. In terms of this sense, the reciting of Tasbih is obvious.
Said in the next sentence 12 is: وَيُرْسِلُ الصَّوَاعِقَ فَيُصِيبُ بِهَا مَن يَشَاءُ (And He sends the thunderbolts and strikes with it whom He wills). The word: الصَّوَاعِقَ (as-sawa` iq) is the plural form of a-sa` iqah which is the name of the thunderbolt that strikes the earth. The sense of the verse is that it is Allah who sends these thunderbolts down upon the earth and, with these, He strikes whom He wills.
The last sentence of this verse is: وَهُمْ يُجَادِلُونَ فِي اللَّـهِ وَهُوَ شَدِيدُ الْمِحَالِ they are quarrelling about Allah, and He is stern in His plan). The word: الْمِحَالِ (al-mihal: with Kasrah on the initial letter Mim) has been used here in the triple sense of stratagem and plan, and retribution and punishment, and in the sense of power as well. The verse means that (it is in the background of what has been stated above) that these people are busy with debates and altercations about the truth of Allah's Oneness - despite the fact that Allah Ta` ala has the ultimate power whose plan overtakes all and nothing works against it.
Tazkirul Quran
Maulana Wahiduddin KhanOn ayahs 13–14
When there is lightning, sometimes it carries the message of pleasant weather. But sometimes it falls on the earth like a thunderbolt and burns things down. Similarly, when the clouds gather, they sometimes shower beneficial rains upon the earth. But sometimes they are the forerunners of storms and floods. This means that in this world, one and the same thing can have the aspects of both fear and hope. The One who manages the affairs of the world sends His blessings to the people of the earth by means of various phenomena. He can turn an ostensibly beneficent thing into the most destructive punishment. This state of affairs warns man that he should never consider himself to be safe from God’s scourge. Heedless human beings always wait for some unique and magical sign. But those whose consciousness is alive are successful in finding every kind of sign—of an inestimable value—in the daily affairs happening around them. They feel their hearts beat faster with the roll of thunder and the flash of lightning and when they look at the raindrops, a flood of tears flows from their eyes. The condition which the angels face on seeing the power of God directly, are one and the same as those faced by true human beings, even when they have not seen the power of God directly.
Uthmani text of the Madinah mushaf (King Fahd Complex). Translation: Saheeh International. Tafsir via Quran.com.