Changing Temperature of a Galvanic/Voltaic Cell: Should I wait for the electrodes to also change in temperature?
In general the higher the temperature of the electrolyte, the more power you can draw from the cell.

The reason for this is, because the ions of the electrolyte can move more freely when the temperature is higher and chemical reactions do in general happen quicker with increased temperature. 

On the other hand side the hotter a metal gets, the bigger its resistance will become. This is because electrons can’t move as freely when the temperature is increased.

However this effect usually is of importance when temperatures are quite high, like in an light bulb.

If you just heat the electrodes for 30-40°C, I doubt you would be able to even measure the difference in resistance (even though it does exist).

So to sum it up, the output power of a cell in relation to the temperature will mainly be altered by the temperature of the electrolyte.