You are asking a very subjective question.
You didn't indicate where you are from; you didn't indicate how cold temperatures you can tolerate. I live in the northeast and work in construction, so I can tolerate lower temperatures much better than most people.
The pools are heated; can you tolerate the walk back to the room if the temperature is in the 50's, even the 40's in the evening.
Secondly, no one can predict the temperature this far ahead (believe me, if I could, I wouldn't be working at all). The best thing is to look at the temperatures before you go and then decide if it is warm enough to swim for you or can you tolerate it if is it cold the walk back to the room.
I have been going the same week almost every year since 2000 and the temperature has rarely been the same from year to year.