Some Jews came to the Messenger of Allaah, sallallaahu 'alayhi wa sallam, and said, “Tell us what thunder is? Muhammad, sallallaahu 'alayhi wa sallam, replied, 'It is an angel from Allaah’s angels that is set over clouds and in whose hands is a Mikhraaq by which he drives clouds away, directing them where Allaah commands him.'”
Is this hadith authentic? Also, what is the explanation of this hadith?

All perfect praise be to Allah, The Lord of the worlds. I testify that there is none worthy of worship except Allah and that Muhammad is His slave and Messenger.

This hadeeth was reported by Ahmad, At-Tirmithi and others, and some scholars classified it as saheeh (sound), such as Ibn Mandah in Kitaab At-Tawheed, Ahmad Shaakir, and Al-Albaani. As-Suyooti stated in Ad-Durr Al-Manthoor, "Imaam At-Tirmithi classified it as saheeh, but the books we have at hand state that he said, “It is a hasan  ghareeb (i.e. it is a good hadeeth that is strange to come from this chain of narration).”

However, some scholars classified it as weak, such as Ash-Shawkaani in his Tafseer (exegesis), as he said, “Its chain of narrators is weak.” 

Shuayb Al-Arna'oot , as well as some contemporary scholars, also classified it as weak in his commentary on Al-Musnad. Their statements on the hadeeth have been published on the internet.

As regards the explanation of the hadeeth, then At-Tanweer Sharh Al-Jaami’ As-Sagheer by As-San’aani reads, “Thunder is one of the angels of Allah who is entrusted with the clouds. He has entwined shreds of fire with which he drives the clouds wherever Allah wills.” [abridged]

As for the famous problematic issue for whoever presumes that there is a contradiction between this hadeeth – if we presume it to be authentic – and the scientific material interpretations of the reality of thunder, it should be noted that the fact that metaphysical reasons are confirmed to us, like the act of angels, is not inconsistent with the material causes of some cosmic phenomena that Allah made; both are preordained and predestined by Allah. For example, everyone dies by the angel of death taking his soul, and this does not contradict the fact that one dies because of a material reason, such as being killed, or due to a disease or otherwise. Ibn Taymiyyah said, “As regards thunder and lightning, then the hadeeth reported by At-Tirmithi and others reads that the Prophet was asked about thunder and replied, 'Thunder is one of the angels of Allah who is entrusted with the clouds. He has entwined shreds of fire with which he drives the clouds wherever Allah wills.' In Makaarim Al-Akhlaaq by Al-Kharaa’iti, it is narrated that ‘Ali was asked about thunder and replied, 'It is an angel;' and he was asked about lightning and said, 'It is entwined fire in the hands of the angels.'” Another narration reads, “It is entwined iron in the hands of the angel.” Other narrations were also reported in this regard.

Statements from some scholars of the Salaf (righteous predecessors) that do not contradict the above ones were also reported, such as the statement: “It is a movement of celestial clouds due to air compression in the cloud. However, this does not contradict that (the metaphysical explanation), … the angels move the clouds from one place to another. Indeed, every movement in the upper and lower World results from the action of the angels.

The voice of a person results from the movement of his body parts, which are his lips, his tongue, his teeth, his epiglottis, and his throat; he, however, along with that, is said to be praising his Lord, enjoining good, and forbidding evil.” [End of quote]

Allah knows best.