The only thing I can recommend for summer is air conditioning. Put cake in fridge until ganache is set but cake not chilled completely. I have had to do a cake here in Australia on a 44 degree day and all I did was kept putting the cake back in fridge for 15 minute intervals to set ganache between coats. I left it in an air conditioned room once covered in ganache to set up then covered in fondant and kept it in the coolest room of the house when air conditioning was off (ie night). The thing to avoid is not to chill cake to centre but just set the ganache. Some people have special fridges that have humidity control so they are able to set their fridge so the cake is kept cool but that no condensation occurs.
