Why would you use まいります for rain? (降ってまいります)


I ran across this example sentence in a basic dictionary, but I can't figure
out what particular meaning まいります has in this context.

[code]

    雨が降ってまいりました。
    
[/code]

Generally speaking, it's used as the humble verb for motion. In this case,
[参]{まい}る replaces [来]{く}る. Why would this be attached to rain? Is there
another meaning or would this simply be a slightly formal way of talking?




I hope that someone can explain this more accurately, but let me try some
explanation.

According to
[敬語の指針](http://www.bunka.go.jp/bunkashingikai/soukai/pdf/keigo_tousin.pdf),
the document explaining the use of honorifics in Japanese written by the
Council for Cultural Affairs, there are two different kinds of what have been
traditionally categorized as 謙譲語 (humble words). Most of them are solely used
for actions/belongings of a speaker or someone considered to be on the side of
a speaker, and those are called 謙譲語 I. However, the other humble words such as
参る and 申す can also be used for actions/belongings of something which is on
neither the speaker’s side nor the audience’s side. In this usage, they play
almost the same role as 丁寧語 (polite words). These humble words are called 謙譲語
II.

Therefore, in the example sentence, 参る is essentially used to make the
sentence simply more polite than 雨が降ってきました.

To emphasize the difference between 謙譲語 I and 謙譲語 II, we cannot rephrase the
example sentence as 雨がお降りしてきました because お…する forms 謙譲語 I from a verb.




I hope that someone can explain this more accurately, but let me try some
explanation.

According to
[敬語の指針](http://www.bunka.go.jp/bunkashingikai/soukai/pdf/keigo_tousin.pdf),
the document explaining the use of honorifics in Japanese written by the
Council for Cultural Affairs, there are two different kinds of what have been
traditionally categorized as 謙譲語 (humble words). Most of them are solely used
for actions/belongings of a speaker or someone considered to be on the side of
a speaker, and those are called 謙譲語 I. However, the other humble words such as
参る and 申す can also be used for actions/belongings of something which is on
neither the speaker’s side nor the audience’s side. In this usage, they play
almost the same role as 丁寧語 (polite words). These humble words are called 謙譲語
II.

Therefore, in the example sentence, 参る is essentially used to make the
sentence simply more polite than 雨が降ってきました.

To emphasize the difference between 謙譲語 I and 謙譲語 II, we cannot rephrase the
example sentence as 雨がお降りしてきました because お…する forms 謙譲語 I from a verb.

