By Kathy McLeish and Patrick Williams

Parts of southern Queensland and northern New South Wales are in for a scorcher, with the Bureau of Meteorology (BOM) predicting severe-to-extreme heatwave conditions from Friday

With temperatures expected to crack 40 degrees Celsius in some spots, we check with the BOM and other relevant authorities to find out exactly you need to know ahead of the heat.

How do you define a heatwave?

It is not just one day of hot weather.

It takes three or more days of high maximum and minimum temperatures that are unusual for the location for BOM to declare a heatwave.

It is calculated using the forecast high and low temperatures over the next three days, comparing this to actual temperatures over the previous 30 days, and then comparing these same three days to the normal temperatures expected for a particular location.

Heatwaves end when the mercury falls to more normal levels.

How can BOM track heatwaves?

BOM launched its heatwave service

The service was aimed at giving communities, government, public health, emergency services and industry enough warning to plan ahead and prepare for the heat.

How deadly can heatwaves be?

According to BOM, in the past 200 years, severe and extreme heatwaves have taken more lives than any other natural hazard in Australia.

For example, 173 people died in the 2009 Victorian bushfires, but 374 people lost their lives in the heatwave that preceded it, according to BOM.

Queensland Health says it is important that your body temperature stays between 36.1C and 37.8C — anything above this may cause heat-related illness.

Who is at risk during a heatwave?

Pretty much everyone, according to Queensland Health

Remember, the best way to reduce the risk of heat-related illness is to drink plenty of water and keep your body as cool as possible.

What is heatwave intensity?

There are three levels, beginning withlowntensity

It is the most common event and the majority of people are able to cope with this level of heat.

Severe heatwaves

Extreme heatwaves

What does it mean for our firefighters?

Nothing good. Hot weather only means heightened fire conditions.

Queensland Fire and Emergency Services is warning residents in affected areas to be vigilant, report bushfires to triple-0, and prepare their homes now.

The Queensland Rural Fire Service has a handy guide for preparing bushfire survival plans

Will power suppliers be able to cope?

Here’s hoping.

Queensland’s Energex say sufficient preparations have been made to cope with the expected additional load

Daily peak demand usually occurs between 4pm and 8pm, when people get home for the day and switch on appliances simultaneously, while network peak demand occurs only a few times a year, usually in cases of extreme temperatures.

The record summer peak stands at 4,760 MW for the summer of 2009/2010.

What can you do before and after a heatwave?

ABC Emergency has plenty of tips:

This post originally appeared on News.

© 2016 Australian Broadcasting Corporation. All rights reserved. Read theDisclaimer here.