Mum's sad tribute to her toddler son, who died in a locked car in 35 degree heat.

The grieving mum of a little boy who died after being left in a hot car, has paid tribute to her son on Facebook.

The 22-month-old twin, called Jone, was found unresponsive in a locked car on Sunday, when temperatures reached nearly 35C.

Emergency services were called to his home in Chester Hill in Western Sydney immediately, but he could not be revived and died. 

On Sunday night, his mother, Samantha Rowlands, shared a picture of her son which she captioned 'my baby' alongside a string of heartbreak emojis. 

Jone, who is the youngest of six children, was reportedly left in the care of someone else while his mother was out on Sunday.

Ms Rowlands was seen running down the street screaming 'my baby' after she was told the news that her little boy had died. 

Frank Ingrati, who lives next door, told the Daily Mail that he is on friendly terms with the family, and said he thought Jone's grandmother and mother lived there together raising the children. 

'They're a really friendly family, keep to themselves, a really nice quiet family where the kids play in the backyard,' he said.

'They give me no trouble at all.'

His grandmother, suffering from shock, after the death was taken to hospital on a stretcher. 

Police said they are still investigating exactly what happens.

'The child had been left unattended, we're still looking into the circumstances surrounding his death,' a NSW police spokesman said.