Help me understand what this is. After playing outside, even in the da…

Help me understand what this is. After playing outside, even in the daytime or evening, at temperatures up to 28 degrees Celsius upon returning home, the child cries intensely, refuses to breastfeed, lasts for 15-20 minutes. I thought it might be heatstroke, but judging by information online, he should be weak and so on. Usually, when they come home, I turn on the air conditioner, either it helps or the child simply gets tired of crying...