The attached Excel spreadsheet generates a graph showing the relation between nitrous oxide bottle pressure and temperature. I don't have a heater (bottle or otherwise) in my car and I wanted to know how colder weather would effect pressure. I couldn't find the graph I wanted so I decided to make it myself. For those interested in the details, the spreadsheet solves an extended Antoine equation to estimate vapor pressure.
Nice, resource...but it seems off. I store all my bottles inside between 65-72 degrees ambient temp and they are never 700+ psi during storage.
The graph is probably more accurate than your pressure gauge. Also the bottle temp may not be exactly ambient air temp. If true bottle pressure is below 700 psi then bottle internal temperature is below 65 degrees.
Funny thing is I was looking for a chart about that very thing yesterday and came across a temp vs bottle pressure chart. I am about to install nitrous kit from Nitrous Outlet on a 2010 Camaro so I wanted to know how temp would effect the pressure since I did not get a bottle heater. Temps where the car is going to be run are usually in the 80-95* all year long.
Nitrous Oxide Pressure/Temperature Graph 
