How Does Heat Impact Your Health?

The amount of heat stored in the human body is determined by a combination of (a) an inability to eliminate internally generated heat from metabolic processes due to environmental heat stress (for example, high temperature, high humidity, low wind, high thermal radiation), (b) clothing creating a barrier to heat loss, (c) external heat gain from the environment.

The body’s inability to regulate internal temperature and eliminate heat gain in such conditions increases the risk of heat exhaustion and heatstroke. The strain put on the body as it tries to cool itself also stresses the heart and kidneys. As a result, heat extremes can worsen health risks from chronic conditions (cardiovascular, mental, respiratory and diabetes related conditions) and cause acute kidney injury.

Deaths and hospitalizations triggered by extreme hot weather occur rapidly (same day and following days), which means interventions also need to be rapid when a heat alert is issued.

Heat can also disrupt and compromise essential health services, such as the loss of power supply and transport. Heat will reduce working productivity and increases the risk of accidents. It is difficult to complete work or learning in very hot weather and heatwaves may lead schools and other institutions to close. Heatwaves can also be associated with hazardous air pollution events.

The scale and nature of the health impacts of heat depend on the timing, intensity and duration of a heat event, and the level of acclimatization and adaptability of the local population, infrastructure and institutions to the prevailing climate.

What actions should the public take?

Stay out of the heat

• Avoid going outside and doing strenuous activity during the hottest time of day.
• Stay in the shade. Remember that perceived temperatures in the sun can be 10–15 ˚C higher.
• Spend 2–3 hours during the day in a cool place.
• Be aware of the risk of drowning. Never swim alone.
• Stay informed about official heat warnings.

Keep your home cool

• Use the night air to cool down your home by opening windows after dark when the outdoor temperature is lower than the indoor temperature.
• During the day when outdoor temperatures are higher than indoors, close windows and cover them with blinds or shutters to block direct sunlight. Turn off as many electrical devices as possible.
• Use electric fans only when temperatures are below 40 ˚C / 104 ˚F. In temperatures above 40 ˚C / 104 ˚F, fans will heat the body.
• If using air conditioning, set the thermostat to 27 ˚C / 81 ˚F and turn on an electric fan – this will make the room feel 4 ˚C cooler. It can also save up to 70% on your electricity bill for cooling.
• Remember that it may be cooler outdoors in the shade.

Keep your body cool and hydrated

• Use light and loose-fitting clothing and bed linens.
• Take cool showers or baths.
• Wet your skin using a damp cloth, spray, or wet light clothing.
• Drink water regularly (1 cup of water per hour and at least 2–3 litres per day).
• Regularly check in with vulnerable people in your circle – especially people over 65 years old and those with heart, lung or kidney conditions, a disability, and living alone.

Protect infants and children

• Never leave children or animals in parked vehicles for any amount of time, as temperatures can quickly become dangerously high.
• Avoid direct exposure to the sun during peak hours, seeking shade or staying indoors instead. Shade can reduce how hot you feel by more than 10 °C.
• Never cover an infant stroller / pram with dry fabric – this makes it hotter inside the carriage. Instead, use a wet, thin cloth and re-wet as necessary to lower the temperature. Combine with a portable fan for even greater cooling.
• Dress children in lightweight, loose-fitting clothing that covers their skin, and use wide-brimmed hats, sunglasses and sunscreen to protect them from the sun’s rays.
• Follow the guidance on keeping your home cool to maintain a safe indoor temperature