فَأَرْسَلْنَا عَلَيْهِمْ رِيحًا صَرْصَرًا (So, We let loose a wild wind on them - Fussilat 41:16 ⧉) This is the explanation of what was mentioned as ` calamity of ` Ad and Thamud' in the earlier verse Fussilat 41:15 ⧉. The Arabic word used in the text is sa` igah. It originally means ` something that renders one unconscious. That is why the thunderbolt is also called sa'iqah, and unforeseen calamity and disaster is also called sa` iqah. The storm which entrapped the people of ` Ad was also a 'sa'iqah', and has been mentioned in the present verse Fussilat 41:16 ⧉ as ` wild wind' which was a wild tempest of extremely high speed and had piercing sound. (Qurtubi)
Mentioning the details of this tempest, Dahhak has said that rains had been totally stopped from them by Allah Almighty for three years, and dry tempestuous winds kept on blousing all the time, and for eight days and seven nights, they had continuous extremely severe windstorm. Some narrations have it that this event took place in the end of month of Shawwal, commenced on a Wednesday and kept on till the next Wednesday. Whenever any nation has been subjected to a scourge, it has happened on a Wednesday. (Qurtubi, Mazhari)
Sayyidna Jabir Ibn ` Abdullah ؓ has stated that when Allah Almighty wants the welfare of a nation, He orders rain to fall on them, and stops very fast winds from blousing over them, whereas when a nation is to face a misfortune, rain is withheld from them, and strong winds start blousing frequently.
فِي أَيَّامٍ نَّحِسَاتٍ (in unlucky days....Fussilat 41:16 ⧉). It is established by the principles of Islam and ahadith of the Holy Prophet ﷺ that no day or night is in itself unlucky or ill-omened. The days of the windstorm over the people of ` Ad have been called ` unlucky' because those days had become ill-omened for them due to their misdeeds. It does not necessarily mean that those days were ill-omened for everybody. (Mazhari and Bayan-ul-Qur’ an). The detailed investigation as to whether anything can be ill-omened by its nature can be seen in the author's book Ahkam-ul-Qur'an Vol. 5 in Arabic)