In the Star Trek movie First Contact, Jean-Luc Picard mentions something about the environment on deck 16 being like a Borg ship. Lt Worf states the temperature as 39.1 degrees Celsius (102.38 deg F) with a relative humidity of 92 percent.
The effective humidex is 69.4 Deg C (156.9 Deg F). This would kill most lifeforms including Picard's crew, with the exception of Lt Data, in a very short time.
How do the Borg and all the assimilated species survive such conditions?
This is simply impossible to answer without opinion based conjecture.
With that said, the Borg are fused organic machines...they will have a specific and optimum temperature at which their organics and machine parts run optimally.
This is normal for all things, including machines, electronics, batteries. and you guessed it, living organisms.
Star Trek is a space show with hundreds of thousands of space aliens that all exist with different requirements. On earth there are plenty of organisms that live in a huge variety of extremes. Space is no different.
Apparently the optimum temperature of Borg existence is 39.1 C and relative humidity of 92%.
