I do not think an analog voltmeter will be affected by the cold.

Great to hear this. This means I may not need to replace the voltmeter
on the dashboard, and can save some money. I thought the voltmeter
might be affected by cold temperature because the instruction manual of
the multmeter tells me not to use it when temperature is too cold.

I would check the wires. How far from the battery? There could be a
voltage drop. What size are they? They may need to be bigger to
compensate for distance. Is there corrosion on the terminals? This will
affect the reading.

Honestly, I didn't even think of checking the connection between the
battery and the on-dashboard voltmeter until you guys have pointed this
out. You guys are probably right in saying that the wiring may be
undersized because I recall that most of the wires inside the
batteries/wiring compartment are kind of thin like those light gauge
wires. I will document all the wiring inside the boat when the weather
becomes warm. For now, I will check the voltage in the voltmeter
terminals to see if the voltage is as low as what is being shown in the
voltmeter.

Does the meter have a calibration screw on it? If it does adjust
it so it matches the reading of the digital at the batteries.

Thanks for this tip. I didn't know that there is such a thing in a
voltmeter. I will find out when I get back home.

Jay Chan