I'm all for pedantry, but any human metaphor is clearly referring to a human perspective, and it's very reasonable to call any temperature that is too high to sustain human life hot.
500 Kelvin is a hot oven that severely burns you if you touch the tray directly. 1000 K is a nice campfire. 1500 K is the upper end of Magma. 2500 K is beyond normal blast furnace temperatures.
The silly thing is comparing the 'temperature' of one's love to it. I mean I get poetic overstatement and I get his idea is to melt the heart of his woman of desire, however this is maybe a bit too literal.