What is a heatwave and how to keep safely cool during one

What is a heatwave and are they increasing?

Heatwaves are prolonged periods of excessive heat that generally last for at least three or more successive days. The Bureau of Meteorology’s heatwave forecasts and warnings are based on a three-day period, comparing against the local climate and past weather (30 days) and accounting for night-time temperatures as well as the daily maximum.

Essentially, the BOM measures how much of a shock to the body the forecast temperatures will be, using an excess heat factor (EHF), compared to the weather over the past month. The heatwaves can be classified as low-intensity (where most people can cope), severe (more challenging for vulnerable people) or extreme (impacting anyone who doesn’t take precautions, even healthy people).

According to Victoria’s Climate Science Report 2024, heatwaves have become more intense, frequent and longer in the state since the 1950s. The heatwave season also now starts earlier.

Monitor weather forecasts and sign up to receive warnings

The best way to stay safe and cool during a heatwave is to be well prepared ahead of time. This starts with being alert to the weather forecast for the days ahead.

You can monitor heatwave warnings issued by the Bureau of Meteorology and freely subscribe to receive alerts whenever the BOM releases a warning for severe or extreme heatwave conditions. The warnings are issued on the bureau’s website, the BOM Weather app and through its telephone audio warnings service.

The VicEmergency app and website is another good resource for alerts on extreme weather conditions, while the Victorian Department of Health also issues heat health warnings when temperatures risk impacting people’s health.

The Department of Health’s Better Health Channel also has excellent advice on how to handle a heatwave and recognise early symptoms of heat-related health problems.

Consider your health and support network

The Australian Red Cross is among a number of authorities offering practical tips to help you prepare for heatwaves and very hot weather. As well as checking the weather forecasts (as described above), these include:

• Speak to your doctor about the potential impacts of heat and precautions you can take, particularly if you have a health condition.
  
• Download the Red Cross First Aid app, which provides vital information to help with common emergencies and safety advice during a crisis.
• Identify your support network – family, friends, neighbours or a caregiver, for example – who can help you before and during a heatwave. This may include adjusting your air-conditioning, closing blinds, doing your shopping and checking in on you.
• Write down important numbers – doctors, mental health services, support network, care agencies, electricity company (if there’s a blackout), etc – so they are easily accessible if you need help. You can also store these contacts on your phone.
• Make plans with your support network about what you will do if you lose power during a heatwave. Identify a place in your local area where you can go to stay cool (such as a public library, community centre, shopping centre or cinema) and decide how you'll let your support network know where you are.

If you or someone in your household relies on life support equipment, you may be eligible for protection under the life support energy regulations. This means that your local distributor should advise you in advance of any electricity outages, and that in the event of an outage your property will be on the priority list for reconnection. Speak to your local energy retailer for more information or visit Arcline by RACV’s Life Support page here.

More: What to do in a power outage or blackout

Prepare your home before a heatwave arrives

There are many ways to prepare your home to make it as cool as possible during the hotter months – and ready for extreme weather events such as heatwaves. Common measures include installing and maintaining air-conditioning units, ceiling fans and outdoor blinds.

It’s important to ensure the AC unit has been serviced and is working well. Always use a qualified professional who can handle servicing, maintenance and repair or replacement, especially if the air-conditioner is older. Modern systems are designed to keep homes cooler while consuming less power. You might also consider how to operate the AC at optimum efficiency, such as leaving it on rather than using it in short bursts. The CSIRO provides advice on this.

A professional tradie can also do an assessment of your home and undertake maintenance tasks to keep it as cool as possible during a heatwave, such as sealing around windows and doors and advising on preventative measures such as double-glazed windows, insulation, light fittings, reflective coatings, external window awnings and blinds and thermal curtains.

You could also prepare a dedicated ‘cool room’ in your home using a combination of AC, fans, curtains and blinds, creating a sanctuary for when the heatwave is at its most intense.

Outside, your plants will appreciate some pre-heatwave planning, such as mulching and heavy watering ahead of the extreme event. You might also move pot plants indoors or under shade, or create temporary shaded areas in the garden using an umbrella or shade cloth, for example. Longer-term planning might involve planting more trees to provide more shade around your home.

It’s also recommended that your vehicle’s emergency roadside assistance and scheduled servicing are up-to-date and that the car’s air-conditioner works well. See our separate guide on how to maintain your car during hot weather.

More: Air-conditioner servicing and maintenance – What you need to know

Stock up on essentials and create a home emergency kit

A little preparation with food, water and other essential items can go a long way to keeping you and others in your household – including pets – cool and safe during a heatwave or other extreme weather events that might last for several days.

A home emergency kit can be especially helpful in an emergency of this nature, or in the event of a blackout. Some essential items include:

• Medications and essential toiletries.
• First-aid supplies.
• Bottled water.
• Non-perishable food.
• Mobile phone charger.
• Torches and headlamps (with extra batteries).
• Copies of important documents.

You might also consider personal cooling products such as an ice vest or battery-powered fans. It might help to have cool bags/eskies and ice bricks ready to cool down water and medications, too.

If you have pets, the home emergency kit should include their food, water, medications and other essential supplies and equipment.

More: Essential items for your home emergency kit

How to stay cool at home during a heatwave

As well as offering tips on how to prepare for a heatwave, the Australian Red Cross and Victoria’s Department of Health provide useful tips for coping when the heatwave arrives:

• Stay inside and keep out of the heat as much as possible. Plan to do most of your activities early or late in the day to avoid being outside during the hottest hours.
• Cancel or reschedule non-essential outings.
• Avoid vigorous physical activity.
• Drink plenty of fluids to stay hydrated, even if you don’t feel thirsty.
• Make sure all curtains are closed and external shade cloths/blinds are in place to shield the inside of your home from direct sunlight.
• Where possible, use a combination of air-conditioning and fans to keep certain rooms in the home cool.
• If not using air-conditioning, open windows during the cooler parts of the day and allow ventilation between rooms.
• Take cool showers or foot baths in cool tap water, splash yourself with cold water (spray bottles are handy) or use a damp cloth or sponge to cool down.
• Wrap ice cubes in a damp towel and drape it around your neck.

More: Hacks to lower your energy bill during hot weather

Closely monitor your pets

Just like us, pets are affected by prolonged bouts of heat. But unlike us, they can’t be relied on to cool themselves down. In a heatwave, ensure your pets are kept in a cool place in the home.

Relocate them to cool, tiled surfaces if needed (dogs and cats are a big fan of this), darkened rooms or where you’ve got air-conditioning and fans. If possible, don’t keep them outside, as even shade and a full water bowl might not be enough during a heatwave. Keep your pets hydrated by checking that their water supply is plentiful.

You might like to drape damp, cool cloths over them for some relief, and it’s worth keeping your ice tray stocked as they make a welcome addition in a water bowl.

Also keep an eye out for signs of heatstroke in your animals. Symptoms include rapid panting, excessive drooling, vomiting, fatigue and/or twitching muscles. Call your vet immediately if your animal is displaying any of these symptoms.

More: How to know when your dog is too hot or cold

Take precautions outside if you leave home

If you must leave your home during a heatwave, there are some important considerations:

• Do not leave children or animals in parked vehicles. Tests conducted by RACV have shown that vehicle interiors can reach more than 70°C in just minutes when the outside temperature is 30°C.
• If you have a car with remote functions, pre-cool the cabin before getting in.
• With other cars, cool down the cabin with the AC before setting off.
• Do not park the car in direct sunlight if possible. Use sun protectors for glazed areas.
• Protect yourself with appropriate clothing – loose-fitting and lightweight.
• Avoid direct exposure to the sun where possible and adhere to the Cancer Council’s ‘Slip, Slop, Slap, Seek, Slide’ mantra (protective clothing, sunscreen, hat, shade, sunglasses).
• Head for air-conditioned places such as a shopping centre, cinema or library.
• Remember to keep in touch with friends, neighbours and relatives, particularly if they’re unwell or isolated.

More: How to keep your car cool in summer and stay safe