Vitamin D supplements for EBF babies didn't become a standard recommendation until my third child. I figured my first two didn't have vitamin D supplements and they don't have rickets. So I doubt my third will either. If I was dark skinned or lived in the extreme northern latitudes, then I might consider it.
I did start taking vitamin D supplements myself though. Turns out a lot of adults are deficient, and I figured why not?
Also, about it being hot out - if you take baby out in a diaper, baby doesn't need much more than 5 minutes a day for sufficient vitamin D. You can break it up into several 2 minute sessions if need be.
Good luck making your decision.