Children are more vulnerable to heat-related illness than adults. Their bodies gain heat faster relative to their size, they sweat less efficiently, and they are less likely to recognise or communicate early warning signs. On a hot day, an active child can move from overheated to seriously ill quickly — which is why recognising the warning stage and cooling correctly matters so much.

Heat-related illness exists on a spectrum — from mild heat cramps to life-threatening heat stroke. The single most important line to understand is between heat exhaustion and heat stroke, and that line is mental status.

The Heat Illness Spectrum

Source: American Heart Association 2024 first aid guidelines; Canadian Red Cross. Altered mental status is the red flag distinguishing heat stroke from heat exhaustion.

Heat Exhaustion: First Aid Step by Step

Heat exhaustion is the body’s warning that its cooling system is being overwhelmed — the child is pale, sweaty, weak, and dizzy, but is still alert and thinking clearly. Treated promptly, it usually resolves without lasting harm. Your job is to cool the child and watch closely for any change in mental status.

1. Move the child out of the heat — into an air-conditioned building, shade, or under a wet sheet with a fan. Stop all activity.
2. Lay the child down and remove excess clothing — down to a single light layer.
3. Cool the skin actively — apply cool, wet cloths to the forehead, neck, armpits, and groin. Spray or sponge with cool water and fan the skin to speed evaporation.
4. Give cool fluids if the child can swallow — small sips of cool water, not large amounts of ice-cold water. An oral rehydration solution is ideal if available. Do not give fluids by mouth if the child is drowsy, confused, or vomiting.
5. Watch for altered mental status — keep cooling and monitor. Symptoms should begin improving within about 15–30 minutes. If the child becomes confused, agitated, or drowsy, or does not improve, treat it as heat stroke: call 911 and cool aggressively.

Source: American Heart Association 2024 first aid guidelines (move out of the heat, remove excess clothing, limit exertion, give cool liquids if the person can swallow); Canadian Red Cross.

Heat Stroke: This Is a 911 Emergency

Heat stroke occurs when the body’s cooling system fails and the core temperature climbs so high that the brain and other organs are affected. The defining sign is altered mental status in a hot or overheated child. Per the American Heart Association, a hot or exerting person with any change in mental status has heat stroke until proven otherwise — activate EMS. Without rapid cooling, heat stroke causes organ damage, brain injury, and death.

While Waiting for Paramedics — Cool First, Transport Second

The single most life-saving action is to bring the child’s temperature down as fast as possible. Do not wait for the ambulance to start cooling — begin now and keep going.

1. Call 911 and move the child to the coolest available environment.
2. Remove clothing to help heat escape.
3. Cool aggressively — whole-body cold-water immersion is the gold standard. Immerse the child up to the neck in cold water if a tub or pool is available. Use the coldest water you can: ice water (roughly 1–5 °C) cools fastest, and any cold water still works if ice isn’t available — don’t delay cooling to hunt for ice.
4. If immersion isn’t possible, apply ice packs or cold packs to the neck, armpits, and groin, cover the body with cold wet sheets, and fan continuously.
5. Protect the airway and monitor breathing. Do not give fluids by mouth if the child is drowsy, confused, or unconscious. Place an unconscious child who is breathing on their side. Be ready to begin CPR if the child becomes unresponsive and stops breathing normally. Keep cooling until EMS takes over.

Source: American Heart Association 2024/2025 first aid guidelines and Canadian Red Cross — whole-body cold-water immersion is the most effective cooling method for adults and children; ice water (1–5 °C) is preferred where available; cool first, transport second.

Babies and Heat: Special Considerations

Infants are at the highest risk of heat-related illness because they cannot sweat as effectively, cannot tell you they are too hot, and depend entirely on caregivers to regulate their environment.

Warning Signs in Babies

• Flushed, hot skin — check the chest and back, not just the forehead
• Unusual fussiness or lethargy
• Rapid breathing or panting
• Fewer wet diapers than usual (a sign of dehydration)
• Sunken soft spot (fontanelle) on the top of the head
• No tears when crying

Hot Car Danger: Never Leave a Child in a Parked Vehicle

The inside of a parked car heats up far faster and hotter than the outside air, even on a mild day and even with the windows cracked — temperatures can climb to dangerous, potentially fatal levels within minutes. Because children gain heat faster than adults, a child left in a hot car can develop heat stroke very quickly. In Canada, leaving a child unattended in a vehicle can constitute a criminal offence and may trigger child-welfare intervention.

• Never leave a child in a parked car — not even for a minute
• Place your phone, bag, or a shoe in the back seat as a reminder to check before locking
• Teach older children how to honk the horn and unbuckle their seatbelt if they are ever trapped
• If you see a child alone in a hot car, call 911 immediately

Note: exact in-car temperatures depend on outside temperature, sun, and vehicle — treat any child left in a parked car as a time-critical emergency. Guidance on child-vehicle safety: Transport Canada; Canadian Paediatric Society.

Prevention: Keeping Kids Cool All Summer

• Hydrate proactively — offer water every 15–20 minutes during outdoor play, even if the child does not ask for it. Avoid sugary drinks and caffeine, which can worsen dehydration
• Schedule outdoor time wisely — avoid strenuous activity during the hottest part of the day (roughly late morning to mid-afternoon) when heat and UV are highest
• Dress light — loose-fitting, light-coloured, breathable clothing, plus a wide-brimmed hat for sun protection
• Take shade breaks — regular breaks in the shade during active play
• Cool down with water — sprinklers, spray bottles, and wet towels are effective cooling tools
• Acclimatise gradually — when a heat wave arrives, reduce activity intensity for the first few days to let bodies adjust
• Heed heat warnings — in Canada, Environment and Climate Change Canada issues heat warnings using region-specific thresholds; take extra precautions with children and infants whenever one is in effect

Source: general heat-safety guidance from the Canadian Red Cross and the Canadian Paediatric Society; heat warnings issued by Environment and Climate Change Canada.