Health authorities has warned people to take care in the soaring heat of Saturday and Sunday especially at outdoor events.

Ambulance Victoria said 400,000 people were expected to attend major events on the weekend, including the St Kilda Festival, the Moama Southern 80 Ski Race, major cycling tours and rides, a dance party, super-kart racing, rugby and speedway events.

Ambulance Victoria's operations manager Paul Holman said people should respect the heat.

"These events mean people are out in the sun for long periods," Mr Holman said.

"Wear loose fitting, light clothing, and drink plenty of water. Some of the events include alcohol. Party safely, and ensure every second drink is water," he said.

Saturday night is not expected to cool off significantly with a predicted minimum of 30 degrees, continuing the danger period.

A state government study found that the 2009 heatwave saw a 62 per cent increase in deaths. Mr Holman has previously said there was increased dangers when nights remained very warm as the body does not get time to recover and cool down.

Mr Holman said if someone was suffering chest pain or other serious medical condition they should call triple zero but for less urgent ailments they should consider calling a doctor, Nurse On Call, a relative or another service.

Mr Holman urged swimmers to swim at patrolled beaches and not to mix alcohol and swimming with a number of drownings and near-drownings last weekend.

Kidsafe has issued a red alert for all parents on child safety during the weekend saying there was an increased risk of serious or fatal injury to children, chief executive officer Melanie Courtney said. She said parents should plan to avoid heat stress.

"Soaring temperatures mean increased activity around water including backyard pools and heightened danger for babies or children left unattended in hot cars," Ms Courtney said.

On Thursday, paramedics were called to six cases of children locked in cars.

Mr Holman said many of them involved accidents where the child and keys were locked in the car, but some appeared deliberate.

"We were called to a shopping centre car park where three children aged under ten were left in a car for up to 20-minutes. A billboard near the carpark was showing a temperature readout of 37-degrees.

"It's never safe to leave people or pets in a car,' Mr Holman said.

Ms Courtney said there had been a number of fatalities and near fatalities involving young children in drowning and fatal driveway incidents in Victoria and interstate in the past week.

"With children going back to school, driveway activity is increasing. Make sure that you know where your children are at all times and if you move your car, take your children with you," said Ms Courtney.