The radiator takes hot coolant from the engine, and circulates it through tiny pipes inside. Cold air rushing into the engine cools the coolant down, where it then flows back into the engine to cool the engine down. This is a normal function which causes part of the radiator to be hotter than another part. This is fine and there is nothing to worry about unless you are overheating.
If the radiator is old and or you feel it must be an issue with the radiator, a pressure test performed by a certified mechanic will provide you adequate detail on whether it is clogged.
One may want to check that their thermostat is not locking (put in warm water and see if opens)
One may also want to check their lower hose (replace and or check). If lower hose collapses proper flow will not be achieved.
9/10 times the culprit will not be the radiator. Be sure, do a pressure test!