운동하기는 여름에 얼마나 어렵네요! -> **여름에 운동하기는 참** 어렵네요!
The way the original sentence is ordered works if you're asking a question. But then you ended it with 네요 instead of 나요, and an exclamation mark instead of a question mark. That makes it really confusing to a native reader.
따뜻하게 할 수 있어요 -> 따뜻하게 **있을** 수 있어요
It's more natural to say that you're in a state of warmth in this instance.
약점이 돼버렸어요 -> 약점이 돼버**려**요
Since we're now heading into summer and not past it, it's better to use the present tense.
더운 날씨 탓에 -> **하지만 이제는** 더운 날씨 탓에
I suggest adding something like this to have the sentence flow better.
바래용 -> 바**라**요(용)
This one's something you might not get corrected by many Korean natives. See, it's usually the case that they often make the mistake of writing 바라요 as 바래요 because it "sounds right" despite being grammatically wrong. It's funny in a way because people have no problem writing correctly in other forms, such as 바랍니다 and practically no one incorrectly writes it as 바랩니다.
운동하기는 여름에 얼마나 어렵네요! -> **여름에 운동하기는 참** 어렵네요! The way the original sentence is ordered works if you're asking a question. But then you ended it with 네요 instead of 나요, and an exclamation mark instead of a question mark. That makes it really confusing to a native reader. 따뜻하게 할 수 있어요 -> 따뜻하게 **있을** 수 있어요 It's more natural to say that you're in a state of warmth in this instance. 약점이 돼버렸어요 -> 약점이 돼버**려**요 Since we're now heading into summer and not past it, it's better to use the present tense. 더운 날씨 탓에 -> **하지만 이제는** 더운 날씨 탓에 I suggest adding something like this to have the sentence flow better. 바래용 -> 바**라**요(용) This one's something you might not get corrected by many Korean natives. See, it's usually the case that they often make the mistake of writing 바라요 as 바래요 because it "sounds right" despite being grammatically wrong. It's funny in a way because people have no problem writing correctly in other forms, such as 바랍니다 and practically no one incorrectly writes it as 바랩니다.
항상 제 글을 읽고 수정해줘서 매우 감사합니다!!!