This gage shows the engine coolant temperature. Under normal driving conditions the gage will read approximately 210°F (100 °C) or less. If the gage pointer is near 260°F (125 °C), the engine is too hot.
It means that the engine coolant has overheated. If the vehicle has been operating under normal driving conditions, pull off the road, stop the vehicle and turn off the engine as soon as possible.
See Engine Overheating for more information.