Think of it this way. Sativa's that grow in tropical jungles deal with heat much greater than 85-90 degrees. What you need to realize is that in a jungle environment, C02 concentrations are naturally much higher then in places such as the average grow room. One reason for this is the mass amount of decomposition of natural plant matter that takes place on the jungle floors. This increases CO2 considerably and allows the plant deal with the greater heat and humidity. As long as you have some sort of a fresh air exchange and C02 enrichment your plants will thrive in higher temperatures.