Both infrared radiation and microwaves warms up objects it meets, so therefore I wonder, is all long wave electromagnetic radiation hot?
And if it is, why?
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Objects are warmed up by electromagnetic radiation if their molecules have absorption bands at the radiation's wavelength and can thus be absorbed and turned into heat vibrations. A lot of materials have good-ish absorption in the IR- and Microwave-regime, thus these radiation regimes can often be used for heating - but this has nothing to do with the "temperature" of the radiation.
The other thing you should ask yourself is whether it makes sense to attribute a temperature to electromagnetic radiation.