– ḍaḥūqan: a cloud rich in lightning.
– radhādh(an): a drizzle lighter than ṭash; ṭash is a feeble rain.
– qiṭqiṭ(an): the tiniest drops; the order of intensity is qiṭqiṭah (tiniest), then radhādh, then ṭash.
– sajlan: according to al-Nihāyah it is “a bucket filled with water,” plural sijāl. Al-Muḥīṭ adds that sajl is used figuratively for a generous gift, and that is the sense intended here.

Someone might think these descriptions of rain conflict with one another, yet they do not. The supplicant is asking Allah to send rain that combines copiousness with gentleness. Lengthy, detailed wording in supplication is permissible; Allah knows best.

What is derived from the ḥadith:
1 – These inherited invocations are the most appropriate for seeking rain; they should be recited in the rain-seeking prayer, the Friday sermon, and at any time when drought and hardship are present.
2 – The requested rain is portrayed as blanketing the whole earth rather than a single spot, its clouds thick with water, its thunder loud and its lightning bright, descending in abundant, forceful torrents, yet—despite that abundance—falling in soft, small droplets so that it spreads gently across the land without ruining crops or toppling buildings.

Beseeching Him by His Majesty and Generosity—“the Possessor of Majesty and Honor”—is among the best means of intercession, for the Prophet ﷺ said: “Persist with ‘O Possessor of Majesty and Honor’” (reported by al-Tirmidhī, 3524), all the more so in this context.