one can also use locative, Şurada yağmur yağıyor , Burada yağmur yağıyor , Orada yağmur yağıyor , they all sound natural to me.
The literal translation of Şuraya yağmur yağıyor would be "Rain is raining to that place" and if you use locative "Şurada" then literal translation would be "At that place, rain is raining"
Oraya is further away than şuraya, just as o is a bit more removed from the speak than şu is.
It all follows a BSO pattern of being farther removed from the speaker. Ben - Sen - O, Bu(raya/rada) - Şu(raya/rada) - O(raya/rada). The pattern also reflects the distance apart your lips are as you say these words, B - S - O.
I do not know if any of these connections are coincidental, but they can be helpful mnemonics.