We always thought heat was a daytime problem. Why the night is no longer our truce.

We always thought heat was a daytime problem. The sun, the shade we look for at noon, the glass of water, the fan running at three in the afternoon. But something is quietly changing, and it does not happen while the sun is shining, but when it goes down. Nights are warming faster than days. For generations, sunset meant relief; today, that relief arrives later and later, weaker, and in many places it no longer comes at all. And that difference, which seems small, changes everything.

Because the night was always our truce. The moment when the body cools down, the heart rests, and the organism repairs the wear and tear of the day. When that truce disappears —when the air in the small hours stays as heavy as at noon and rest becomes impossible— the body never fully recovers. Stifling days followed by nights without relief, strung together for weeks. In some regions of the world, that siege can last almost all year. It is not just heat: it is constant pressure that never lets up.

And the most revealing thing is not how much the temperature has risen, but how many people it now reaches. What used to be a punishment for a few corners of the planet now touches a large share of humanity. Hundreds of millions of people who half a century ago did not know this kind of heat now live with it as a normal part of their year. Heat is no longer an exceptional event, an anecdote from a particularly harsh summer; it has become one more season: long, recurring, here to stay.

And here comes the dimension that should give us the most pause: who suffers it. It is children who carry the most unfair burden. Their small bodies regulate temperature less effectively, and what is discomfort for an adult can be a real danger for them. They are growing up in a world where sleeping through a cool night —something their grandparents took for granted— is becoming a privilege. They inherit a hotter planet without ever having had a voice in the decisions that heated it.

What is unsettling is that this is no longer the future. As we write about it, France is living through the most extreme heat wave in its history, with dozens of deaths and millions of people on alert. We are not talking about projections for the year 2100, but about what is happening this week, this summer, in cities we believed were prepared. Chronic heat does not knock loudly at the door: it settles in slowly, normalizes the abnormal, and one day we discover that what we called a “heat wave” simply moved in for good.

Perhaps the real reflection lies not in the figures, but in what they reveal about the way we inhabit the world. We build asphalt cities that trap heat, we depend on air conditioning that consumes the very energy that feeds the problem, and we keep measuring the climate by the midday temperature while the real danger grows in the small hours. The question is not whether the planet is warming —that is no longer up for debate— but whether we will have the clarity to adapt before the night, that age-old refuge for every form of life, stops offering us rest. At Semiversal, we follow this phenomenon closely through our climate change indicator, because understanding where it is heading is the first step toward not arriving too late. Because when not even darkness gives us a truce, there is nowhere left to hide.