I found a bug and it may not even be your bug as there are several mods involved. Guessing it's pretty rare so you may not want even to bother with it:

In certain situations it seems that butane gas can have a really weird temperature readout.

I am using Factorissimo 2, I dont know if that is related. The other one noted on the screenshot is Squeakthrough and of course this mod. I've linked it here as this is how the butane was stored so my best guess is that it's pressure tank related but i've almost done paper rock scissors to pick which mod did it!

I have a large store of Butane gas in a Factory building and the gas apparently has a temperature of minus one billion gazillion (or at least a number too large to comprehend). See screenshot link below.

If I make fresh butane, it's fine and I dont see how it ends up like this unless I add it to this storage - If I mix fresh butane with this infected butane it takes on the properties of it.

The number is constantly changing as more gas is added both up and down and it affects all the tanks and in fact all the gas in the tanks so if its piped out of the building, it still has the very long minus number (the red in my screenshot blocks the minus but in other views you can clearly see its a long minus number). If the gas is left alone in a pipe (inside or outside the Factorissimo factory) with no input or output, then the number stays stationary but still not normal temp. I.E. If I pipe the gas out of the Factorissimo2 building, it still stays 'infected'.

Weird huh? At some point i'll process this gas into something sensible & at that point will see if it happens again once I refill the store of it or if I can see what causes it. Until then, I thought i'd just flag it up:

https://drive.google.com/open?id=1jsFXYCMrypdg6SmERbGLmPP7DcfphLPP

Factorio: 0.16.36-2
Factorissimo2 2.2.2.3
Angels Petrochem: 0.7.6
Angels Pressuretanks: 0.3.0
Squeakthrough 1.2.2

Cheers