If fire illuminates your face, you're going to feel hot. Sometimes you start to flush when you're embarrassed and it just feels like there is fire making your face light up.

The readings for this word are both kun'yomi readings. You haven't learned this reading for 火 yet, but it's easier to remember this with a mnemonic for the whole thing:

When are you going to feel hot? When is your face going to flush? When I ask you to go to a hotel (ほてる) with me!