PV=nrT
As the Temperature decreases so will the Pressure, given the same Volume. So yes, you may notice a slight decrease in tire Pressure, that will increase (all by itself) when you warm up the gas in the tube.
That being said, I doubt it is enough to matter.
I wish 40-55 was "cold" too!
it is 35 here this morning, so I guess I have to put on some leggings and a long sleeve jersey. I use CO2 on all my rides, and in the winter below zero is not uncommon.
zac
You quoted the ideal gas law; however the CO2 cylinder contains liquid and saturated vapor much like a propane cylinder or butane lighter. In this case it is the vapor pressure that is of interest. You can look this up on line but for CO2 it is around 800 psi at room temperature and drops to about 600 psi at 40 degrees F. Obviously this is still way above the desired tire pressure so there will be no problem with inflation.