A number of young children have died this year across Australia after being left on their own in a hot car, while police were recently called to rescue a Central West girl who had been left in a vehicle.

Fire and Rescue NSW Station Commander Captain Keven Verhoeven said in hot conditions the temperature inside a locked car will quickly soar to a life-threatening level.

To demonstrate just how deadly leaving a child in a car can be during hot weather, firefighters recently parked a car outside in the direct sun for one hour on a hot day.

The chilling video demonstration depicts firefighters using a thermal imaging camera to measure the temperature inside - it was 100 degrees.

"Children are more sensitive to the heat than adults as their body temperature can rise three to five times faster," Captain Verhoeven said.

"This puts them at a greater risk of heatstroke and other health risks as their body temperature reaches dangerous levels much sooner

"If you notice that a child has been been left unattended in a vehicle call triple-0 and ask for the fire brigade."