"Hotblood" is a term common to all the Five Known People, and basically refers to puberty, when your body's in that transitional period between child and adult, there are all sorts of bodily changes and hormones really go wild. It's a natural thing that everyone has to go through, even if it can be a very trying time for the youngsters and their families alike. Of course, it's extremely individual just how long the Hotblood stage lasts, or how strongly it's felt, but nobody escapes it entirely.
For humans, the Hotblood stage is on average during their teenage years.
For dwarfs and wights, it tends to begin in their late teens/early twenties and end in their early thirties.
For elves, it's a lot more individual, but a good rule of thumb is that it begins around age fifty and ends a couple of decades later.
And of course dragons follow their birth forms in this respect.