Is it necessary to repeat the remembrance, "Exalted is He whom the thunder praises with His praise, and the angels from fear of Him," if the thunder continues, or is it sufficient to say it once?

No specific supplication has been authentically reported from the Prophet, peace and blessings be upon him, to be recited upon hearing thunder. However, it has been authentically narrated from Abdullah ibn Al-Zubayr that when he heard it, he would stop speaking and say: "Exalted is He whom the thunder glorifies with His praise, and the angels from fear of Him" (Quran 13:13). Then he would say: "Indeed, this is a severe warning to the people of the earth." It is recommended to recite this remembrance upon hearing thunder, and repeating it three times is also recommended, as it was authentically reported from Ka'b and affirmed by Umar and Ibn Abbas. A weak hadith has been narrated from the Prophet, peace and blessings be upon him, that upon hearing thunder and lightning, he would say: "O Allah, do not kill us with Your wrath, and do not destroy us with Your punishment, and grant us well-being before that." Acting upon this in matters of virtuous deeds is permissible by scholarly consensus.