I inspect semi tractors trailers and have come across a few LEDS that have actual got hot enough to burn their plastic enclosures , this is a 12 volt system with 20 amp fuse.
Yes, that's perfectly possible - but also an indication of very poor thermal design!
I have been mucking about with a high-power (90W) led module lately and at one point I forgot to cool it while running a brief full power test. Well, that module left a very 'nice' imprint on my thumb when I touched it...