It's getting warm lately./It's getting warm these days.
It's gotten warm lately./It's gotten warm these days.
When you are talking about the weather, seasonal change say from winter to spring, are these expressions grammatically correct? If not how would you normally say?
Just so you know, I'm not a teacher.
The first sentence would be appropriate if the weather was not warm before and it is getting warm (i.e., it has NOT fully gotten warm).
The second sentence also would be proper if the weather was not warm before and suddenly got warm (i.e., it has fully become warm).
Personally, both are correct. It just depends on the context.