A heatwave is when the maximum and the minimum temperature is unusually hot over a three-day period, for the location that we're looking at. That's considered in relation to the local climate, but also into the recent past.

Heatwaves are classified in three ways: there's the low-intensity heatwave, the severe intensity heatwave and the extreme intensity heatwave. And those are coloured so that we can raise people's awareness of the rising intensity of heatwaves.

A low-intensity heatwave is something that we expect people to see most of the time during summer, so the majority of people are likely to have little problems with those heatwaves.

Severe heatwaves are less frequent and are likely to be more challenging for the elderly, particularly if they have pre-existing medical conditions. Extreme heatwaves are quite rare and they can affect the reliability of infrastructure such as power and transport.

Extreme heatwaves are a problem for people who don't take precautions to keep cool. Even the healthy are at risk. People who work or exercise outdoors are particularly vulnerable.

In heatwaves, the hot nights are possibly much more important than the hot days. The inability to recover from the heat of the day puts much more stress on the body.

We need to remember that the impact of severe and extreme heatwaves can be very serious, so listen to the emergency services and health authorities, who can guide us on how we should respond to heatwaves.

The Bureau of Meteorology provides a heatwave service that runs from November until the end of March. The maps provided in this service show the location and intensity of recent heatwaves, and any forecast heatwaves for the next seven days.

Advance notice of severe and extreme heatwaves gives the emergency services, health authorities and the community the opportunity to prepare and reduce the level of impact on people, business and industry.
For more information about heatwaves, visit bom.gov.au/australia/heatwave.