Yes but it will cool down
Do it when the car is cold if the radiator is hot fluid may be forced out when you take off the cap.
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.
there is something wrong with your car. It's not supposed to run and its not supposed to be hot at the same time. Maybe its running for a fashion contest
Hot water in the radiator is under pressure and can burn you.
most likely it will be hot so put snow on it
In a radiator, the fluids get really hot, when things get hot they expand and then they have to go somewhere, the fluid goes into an overflow.
Bad thermostat, fans not working or coming on when they are supposed to, bad waterpump, bad radiator or radiator cap.
cold. If you open the radiator when the car is hot, it can spray all over the place.
Thermostat and radiator
To replace a radiator on a 200 Buick Regal is not really that hard. You will need to remove all belts attached to the radiator and then unscrew the bolts that are holding the radiator. Make sure the car/truck has been off for a long period and the radiator is not hot.
There are plenty of ways a car can break down without the radiator being a part of the cause. As for the reason you'd see steam from a radiator, it would escape if there was a leak in the radiator or the hoses, or if the cap was opened. The contents in a radiator are very hot - hot enough to produce steam.
If your radiator is leaking then you will need to replace it. Additionally, if you find that your car is constantly running hot you will need a new radiator.