"I take off my clothes in the summer."
It can be. The difference here is that by using は, you are introducing summer as a general topic (& leaving context to make clear that it is the time of the action), wheras when using に, you are not introducing a new topic, but make it explicit that summer is the time ("temporal location") of the activity.
Remember that は is the topic marker, not the subject marker.
The subject marker (i.e., the particle that would mark the taker-off of the clothing) is が.
There is no が in this sentence, though, because the subject is left unstated. The Japanese language often omits the subject, if it is obvious or can be surmised.
If someone talks about performing an action, and it's not clear that they are talking about someone else, you can usually assume that they are talking about themselves.
は is the for topic of a sentence. If we said このねつはさむいですね、then we'd be speaking about summer, but we are not. We are speaking about ourselves and our actions. I'll double check with my Japanese teacher, but I'm almost certain this grammar is incorrect. You wouldn't say 明日は本を読みます。you'd write 明日本を読みます。and I'm sure this the same rules apply here.
夏で〜 was rejected here, but i honestly thought that was the correct usage of で
Am i wrong here?