Okay, the temperature of where the T5 linear fluorescent bulbs are most efficient at 35 Degrees Celsius. I was wrong about the T8's being the same as T5, but I still wouldn't use the T8's due to some reasons. T8's and T12's are most efficient at 25 Degrees Celsius.

"It is smaller than T8 and T12 lamps, with a miniature bi-pin base. It is notable for its lumens-per-watt efficiency, due to its peak light output occurring at 35 °C (95 °F) air temperature."
Source