For mine cold has nothing to do with it. My jeep, cold warm don't matter, when its 1/2 full, I can take a corner, look down and i'll be on E! 3 minutes later its back to 1/2. I putt around till it really is on E and go to fill it up, it doesn't show full till 5 or 10 minutes later.
The fuel guage works off of ohms. For most chrystler and many ford vehichles it works:
73ohms Reads empty 8-12ohms Reads full
GM Vehicles and others
0ohms Reads empty 90ohms Reads full
There is a winding of wire and a brush that slides from 1 end to the other. Most look very different but the concept is the same. The higher up the winding the more ohms that should be presented. But sometimes the ohms increase, or decrease. Or the brush breaks, or the coil corrodes. Causes issues with reading.
You can test to see if it is your guage simply by applying ohms of resistance to your fuel guage. If it responds accordingly, then its not your guage it is probably your sending unit in your tank. You will have to drop your tank, and pop out the unit to see if you can replace it.
Here is a picture of the windings
Here is a picture of a typical GM type sending unit, its the half dome silver thing at the end of the float.