What's the lyrics to Onra's "Like the Seasons"?
It's perhaps Shanghainese Mandarin. This song tries to create an old atmosphere from the early 20th century in Shanghai. Onra probably intentionally make it very blurred and unclear. But back then, people who do not live in Beijing their Mandarin accent is not accurately. They would mix their hometown local accent with the standard Mandarin accent. 

After listening this song couple times. As a Shanghainese, it sounds like "我...在怀念你" (I'm missing you) to me.Some comments under 网易云 also mentioned this. In the song, "我" sounds like "吾", which is close to its Shanghainese pronunciation; and "怀念" also sounds close to Shanghainese. So it's a Shanghainese lady speaking Mandarin. However, I cannot give you a 100% sure answer.