Insufficient water flow, air flow over the radiator, slipping belt, head gaskets bad etc. TAke your pick.
pot
replace your radiator cap...
Try a new radiator cap.
hot or cold air
Can be the thermostat which is cheap to replace, or it might be the head gasket which is expensive.
Water under pressure has a higher boiling point, if the water is already hot enough to boil it will suddenly erupt when the cap is removed and pressure relieved.
Normal causes are low coolant and an inoperative radiator fan.Normal causes are low coolant and an inoperative radiator fan.
you need a new radiator cap
Low coolant, inoperative radiator fans, stuck thermostat, failed water pump, restricted radiator, head/headgasket.
when your engine is hot it causes the water to boil and the water and the anti freeze will come out of the overflow pipe.
It could be that the radiator cap is not able to maintain pressure. Check the radiator cap for cracks or any other damage. Replace if necessary. DO NOT remove the radiator cap when the engine is hot.
It could be low on water and stuff, fill it.