Does anyone have any idea why my hot water would suddenly be hotter (quite a bit hotter) than usual? No one has touched the water heater (I don't even know where the temperature setting is). We've had quite a few electric surges lately, but I can't imagine why this would have anything to do with it. Thanks.

Check the condition of your anode rod? If it is severely encrusted with hard water scale it may be building up excess heat? Not sure of this. I am a layman. If you have a water heater manual, get familiar with it. In the meantime. Be careful if you have elderly, young, or folks who have decreased sensitivity to hot that no one gets burned.

Electric water heater? Age?

Your thermostat on the electric heater may be failing and not maintaining the setting. The anode would not affect the temp nor would a power surge.

Where is the thermostat located on most water heaters? My water heater is about 3 years old. Also, my manual say that the high temperature limit switch might be activated - but I can't figure out where the switch is?! Should I call a professional?

Make sure you kill the power and even test after you think you are sure. The thermostat is located under a small panel screwed to the side of the tank. The plate is about the size of TV Guide.