On the hottest days last summer, Lyndsay MacKay would arrive at her 16-month-old son's daycare to find him in a diaper, his skin sticky and his hair plastered to his head.
He would collapse in her arms. Some nights, he'd fall asleep at the dinner table.
She said she knew the educators were doing what they could: ice cubes in the water tables, offering popsicles, darkening the rooms and placing cool cloths on the infants and toddlers.
"But at the end of the day, they're still hot, they're sweaty, they're exhausted," said the Toronto mother and early childhood education professor at Humber Polytechnic.
"From a health and safety and from a development perspective, the children are not — the children are almost just surviving the day."
MacKay is among the growing number of parents, educators, health and legal advocates across Canada lobbying for maximum indoor temperature at daycares, likely 26 C, akin to standards adopted for long-term care facilities in Ontario.
Like seniors, infants, toddlers and preschool-aged children are at a higher risk of developing heat exhaustion and its more severe form, heatstroke.
In part, it's because they have a higher metabolism than adults, creating more heat in their bodies. And, since their sweat glands are less efficient, it's harder to cool down. Plus, babies and young toddlers can't tell caregivers they're overheated.
Even preschoolers likely can't recognize what's happening, said Dr. Kirstin Weerdenburg, a pediatrician in the emergency department at Halifax's IWK Health Centre.
"They don't have a way to explain how they're feeling, so it's [about] knowing their behaviours and all those other physical signs and symptoms," she said.
"If someone's not paying attention to that, they might get, you know, looked over until you get to the more extremes."
In young children, Weerdenburg said, symptoms can look like fatigue, flushed skin, irritability — even having trouble walking, which is a sign of dizziness.
But heat illness presents on a spectrum, so if kids are acting out of character on a hot day, she said it's worth paying attention.
Kids can often be treated at home with fluids and a cool room. But extreme cases of dehydration can make babies or young children too tired to drink, so they require IV fluids, the pediatrician said.
In the most severe cases, organs like the liver and kidney can shut down as the body redirects blood to the skin to help cool it. The heart speeds up, causing an arrhythmia, as it tries to pump more blood faster.