It’s been a scorcher in London this week, with temperatures reaching an alarming 36.1 °C in June—an event so rare that the Met Office recorded it as the highest ever for the month.

The rising mercury isn’t just uncomfortable; it’s dangerous. Heat waves are implicated in cognitive decline and can be lethal, especially for those living with mental health disorders or children.

Studies show that extreme heat can disrupt brain chemistry, altering neurotransmitter levels like serotonin, which may affect our mood and behaviour. For children, the stakes are even higher; a 1 °C increase in temperature is linked to a 2.97% rise in suicide rates among those aged 15 to 24.

The urgency of this issue cannot be overstated, particularly with climate change projected to exacerbate heat waves, potentially exposing young people to seven times more such events than their grandparents experienced.

Scientists are racing to understand the mechanisms behind these effects. As Catherine Thompson from Liverpool Hope University notes, it’s a complex problem that can’t be easily replicated in labs. But every study brings us closer to knowing how—and why—heat affects our minds so profoundly.