소나기가 내리다/오다 (so-na-gi-ga nae-ri-da/o-da) – showers (rain is falling)
This phrase is basically a variation of 비가 오다. It can be considered as a more elegant way of describing a rainy weather/day.
소나기가 내리다/오다 is very similar to 비가 오다 in that you realise that both 소나기 (showers) and 비 (rain) have subject markers attached.
Both phrases literally mean that the showers and rain are falling down, which explains the subject markers.
Other than that, 소나기가 내리다/오다 is a pretty straightforward phrase.
아침에 하늘은 분명히 맑았는데 왜 갑자기 소나기가 내렸네?
The sky was clearly very bright in the morning, why is there a sudden shower?
지금 밖에 소나기가 내려서 이 우산을 가져가세요.
It’s showering outside right now so take this umbrella with you.
중학년 시절에 소나기가 내릴 때마다 죽마 고우들과 밖에서 놀곤 했어요.
During my middle school days whenever it showered, I used to play with my old friends outside.