What extreme heat does to children's brains.

The developing brain is more vulnerable to heat stress than the adult brain, for three reasons. First, children have a higher surface-area-to-body-mass ratio — they absorb heat from the environment more rapidly and lose heat from the core more slowly. Second, children's thermoregulatory systems are less efficient — they sweat less, their blood vessels dilate less effectively. Third, the developing brain depends on a narrower temperature range for optimal function.

What this means practically: at temperatures above 35°C, children show measurable declines in cognitive performance — processing speed, working memory, attention — within approximately ninety minutes of exposure. Above 40°C, these declines become significant within thirty minutes.

Children cannot reliably detect or report their own heat stress. They feel tired, irritable, and unfocused — which parents often attribute to something else.

I want to name the combination of heat and poor self-reporting, because it produces a specific situation: the child who is cognitively impaired by heat does not know they are cognitively impaired by heat. They just feel bad and act accordingly. The parent looking at the irritable, unfocused child attributes this to mood or behaviour. Neither parent nor child has the correct model of what's happening. Neither has the correct model.