Temperatures have passed 40 degrees across regional areas today, with the latest weather observations from the Bureau of Meteorology showing tops in excess of 44 degrees in some places.

In Mildura, the temperature is expected to hit 44 degrees today, with 43 expected in Swan Hill and Nhill, 42 in Horsham, 41 in Echuca and 40 in many other cities and towns, including Bendigo, Shepparton, Warrnambool and Rutherglen.

V/Line trains across Victoria will be running at a slower speed, as required when the temperature hits 36 degrees. The speed restrictions occur between noon and 8pm.

NSW Health says a heatwave in Sydney in 2011 was responsible for the deaths of 96 people and has urged people to keep an eye out for vulnerable members of the community over the next few days.

"The heatwave that affected Sydney in February 2011 ... is a stark reminder that extreme heat presents a real and potentially life-threatening risk," said NSW environmental health medical adviser Richard Broome.

Dr Broome said heat-related illnesses could affect anyone but certain groups were particularly vulnerable.

These included the over-75s, infants and children, people with a chronic medical condition and people who live alone, he said.

"Heat puts a lot of strain on the body and can cause dehydration, heat exhaustion and heat stroke," Dr Broome said.

"It can also make underlying health conditions worse."

Bureau of Meteorology maps showing predicted temperatures for the next three days. The darker the colour, the hotter it is predicted to be in that area.

Across the country, regional areas are doing what they can to avoid the worst of the heat, while authorities warn of dangerous fire conditions.

Western Advocate (Bathurst): Water bill hits $40,000 a day during the dry spell

The Warrnambool Standard: Region braces for 40-degree scorcher, Temperatures soar in south-west

The Courier (Ballarat): Hot stuff: prepare to swelter today

Northern Daily Leader (Tamworth): Hot days for first summer weekend

Murray Valley Standard: Hot weather warning for South Australia

Tips for beating the heat from NSW Health