With regards to exposing something of your body to the rain, this Sunnah can be practised by unveiling any portion of the body, like one’s head or arms or foot or the likes.

One should not expose one’s Awrah in front of others in practicing this Sunnah. And one should avoid standing in the rain if it may cause harm or sickness to oneself.

🌧️🌧️🌧️

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On the authority of Anas ibn Malik radiallahu anhu who said:

A shower of rain fell on us when we were with the Messenger of Allah (ﷺ). The Messenger of Allah (ﷺ) went out and removed his garment till some of the rain fell on him. We asked him; apostle of Allah! Why did you do this? He replied: Because it has recently been with its Lord” [Saheeh Sunan Abu Dawood no. 5100]

Shaikh Bin Baz rahimahullah said:

“So that proves that it is recommended for a person to uncover something of his body like his forearm or his head so that the rain can fall on it as the Prophet (ﷺ) did. So it is legislated for the Muslim to uncover the turban from his head or the edge of his upper garment from his limb or his forearm so that the rain can fall on it or his shin or whatever resembles that from the things that are permissible to uncover in front of the people, such as the foot or shin or head or hand the likes”

[https://www.alifta.net/Fatawa/fatawaDetails.aspx?BookID=4&View=Page&PageNo=1&PageID=2229]

Translator’s Note:

Shaikh Ibn ul-‘Uthaymeen rahimahullah also mentioned it is not from the Sunnah to remain in the rain continuously. The narration says that some of the rain fell on him, not to remain in it. He also said that the jurists said a person can go out into the rain, if he is indoors, in order for the rain to fall on him [See here: https://alathar.net/home/esound/index.php?op=tadevi&id=2294&coid=35507]
And Allah knows best

Translated by
Faisal Ibn Abdul Qaadir Ibn Hassan
Abu Sulaymaan

{End Quote: as taken from https://darussaafi.com/?p=1644}