People are being urged to keep an eye out for the elderly as temperatures soar across many parts of Australia.

Firefighters are on high alert with parts of Australia tipped to have a string of days above 40C, notably in South Australia and Victoria.

Victoria is set to experience its longest stretch of heat and some of its worst fire conditions since Black Saturday when 173 people died.

Many towns in eastern Western Australia and western Queensland will also feel the heat, with temperatures set to soar into the 40s in parts of both states.

National Seniors Australia Chief Executive Michael O'Neill said on Thursday that people aged in their seventies and above were most at risk in severe heat.

"With this hot and humid weather we are expecting, we are asking people to check on their elderly neighbours and relatives to see if they are coping with the heat and if they need help."

Mr O'Neill said it was good to get elderly people out of their homes into cool places with air-conditioning as well as make sure they drank plenty of water and opened their windows and doors during the day.

"We've heard of cases where elderly people have been cooped up at home, with all their doors and windows locked 24/7, and have subsequently died from heat stroke."

Federal Emergency Management Minister Nicola Roxon on Thursday urged Australians to be prepared for disasters with an increased risk of bushfires due to hot and dry conditions in many areas of the country.

She said people should be aware of fire bans and warnings in their areas and keep up to date with weather forecasts.

"Preparing an emergency kit that includes items like a battery-operated radio, torch, first aid kit and medications is a good idea," Ms Roxon said in a statement.