it doesn't affect the gauge, it affects the way CO2 wants to go from liquid to gas state. the cooler, the less it wants to convert, so pressure drops.
leave a CO2 tank in direct sun, and it can blow its safety valve as pressure increases.
Primary: English Mild
On tap: Pale Ale, Lancelot's Wheat, English Brown Ale, Steam Beer, HoovNuts IPA
Bottled: MOAM, Braggot, Raspberry Melomel, Merlot, Apfelwein, Pyment, Sweet mead, Cabernet
Gal in 2009: 27, Gal in 2010: 34, Gal in 2011: 13, Gal in 2012: 10