Readings & Meanings:
あつ（−い） heat, hot (TO THE TOUCH)
ねつ fever, heat, hot, craze
(From a PDF on children's fevers, can't link to it: www.kcif.or.jp/jp/benri/medhical-PDF/10-3.pdf)
Because digestion is hard when the fever is high, do not uselessly force (the child) to eat.
Hideyo Noguchi passionately studied yellow fever; due to that, however, he lost his life.
Wait a minute, there's a bunch of other kanji in this kanji! There's 土, there's 丸, and there's 火.
What, you don't see 火? Well... you're right. It's not exactly 火. It's called "rekka" and it's the little dots of flame under the rest of 熱. It's a radical, and it belongs to the "hi" or flame group.
Other kanji with rekka: 点 、然
Remember that radical I discussed above? Use it to remember that this 熱い has to do with hot things, like water and food. Think of this 熱い as a result of using a gas stove to heat up your dinner.
Also, think of touching the four flames under 熱. Ouch! That's hot to the touch, right?
Easy Kanji, by Fujihiko Kaneda (Amazon Link)