It,s circulated there from the hot engine block and cylinder head by the pipes, hoses and the engines water pump. It could be up to 230 deg F
When a car is hot, keep the car running and add water to the radiator. When a car is cold, you can simply put the water into the radiator.
remove your radiator form your car then poor some hot water in radiator till water comes out nice and smooth.
Thermostat and radiator
The radiator cools the water which then goes to your engine to cool it off, as cool water enters your engine hot water from the engine enters your radiator
Hot water in the radiator is under pressure and can burn you.
This is likely a stuck thermostat.
It can mean that the temperature is too hot or you have a bad radiator cap.
The most common reason for overheating of a car radiator is that there is not enough water in the radiator. Radiators can lose water in a variety of ways, and often need to be refilled. The other possibility is that the water is not being circulated properly. I should add that cars do heat up quite a bit in the sunlight on a hot day, which adds significantly to the chances of overheating the radiator.
It is not so much the temperature of the water but the pressure that the hot water produces. If you will look at almost any car radiator cap you will notice a warning that says something to the effect'warning contents under pressure. Do not remove when hot.'
Turn it off. Let it cool off and then see if it has a coolant leak or radiator leak. Don't open the radiator when hot because the hot water will spray out.
Do it when the car is cold if the radiator is hot fluid may be forced out when you take off the cap.
You say it's running hot, so i am assuming you have hot water in the radiator. If the thermostat was not opening, there would be no hot water in the radiator. Since the temperature sensor is on the engine, it reads the temp of the water in the engine. (Not in the radiator). The fact you have over heating tells me the water is getting hot but the sensor is not reflecting that. I would say it's either the sensor, or the gauge.