Pet peeve of mine too - you'll never get close to that in summer here without a water chiller. I settled on 75F because I can (almost - occasionally ambient solutions will be 76-77 in the worst of summer heat) always use my Jobo to heat UP to that temperature.
Fortunately Ilford publishes a neat chart that makes equivalent conversion for starting points simple, then after the initial conversion I fine tune as usual except using 75F.
Wow! Why don't you have an air conditioner?
~Stone | "...of course, that's just my opinion. I could be wrong."~Dennis Miller