A heatwave warning has been made after a portable air conditioning unit burst into flames in the middle of the night.

Ainsley Lewis and her husband bought the unit for their Oakridge Park home in a bid to keep cool during the sweltering temperatures.

But at around 3am on Sunday morning it suddenly caught fire, with no warning, while they slept.

"Thankfully, my husband woke up in time and managed to drag the burning unit downstairs, out of the house and extinguish the fire,” said Ainsley, who is a microblading brow artist.

placeholder image — The burnt out remains of the unit

"The fire brigade attended afterwards to check the smoke damage and make sure our home was safe.”

A video shows the flames shooting from the unit and a small explosion when it was outside.

“We feel incredibly lucky — had my husband not woken when he did, the outcome could have been very different,” said Ainsley.

"We live directly next to the park, so with the current hot and dry conditions, there was also a real risk of the fire spreading outside and becoming catastrophic.

“We want to warn other families using portable air conditioning units, especially overnight during hot weather, to be extremely careful.”

Fires in portable air conditioning units can be driven by electrical overloads, improper connection to extension leads, or mechanical failure in the compressor.

People should always plug the unit directly into a primary wall socket and never use extension cords or surge protector strips. Air filters should also be washed or replaced regularly to ensure smooth airflow.