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?
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.