Her mother, Lesley Brown, told reporters on Sunday she was sick to her stomach with worry.

"Every hour she's gone it's just making it worse," she said.

Temperatures have plummeted to minus two in the area where she is thought to have gone, and her mother said she didn't know how anyone could survive the conditions.

"If she was out in the cold, I don't know how she would survive," Ms Brown said.

“It's like minus two here at night. How could anybody stay safe in that situation?"

Jodie's aunt, Tracey Grice, also made a tearful plea, saying they only wanted Jodie to return home.

"We just want to know you are safe and warm," she said.

Ms Brown described Jodie as happy-go-lucky and sporty; a "very friendly, happy girl".

Her behaviour had been "a bit moody" a couple of weeks prior to her disappearance, but normal in previous days, she said.

The distressed mother pleaded with her daughter to let family members know she was safe.

"We miss you badly baby. We miss you so much. We just want you to come home but if that's not possible at the moment please ... just let us know you're safe," she said.

Anyone with information on Jodie's whereabouts can call Kyneton police on 5421 2900.

SUNDAY: A 13-year-old girl has been missing for three days after running home from a bus stop in central Victoria.

The family of Jodie Binks-Brown, along with police, have pleaded for help to find the missing schoolgirl, who hasn't been seen since early Friday morning.

"Police have concerns of Jodie's welfare, given her young age," said police spokeswoman Natalie Webster.

"She does not have a phone or access to money."

Jodie had been waiting for the school bus at 7.45am on Friday with her brother in Romsey, in the Macedon Ranges, when she told him she had forgotten her shoes and needed to run home to get them, police said.

She never returned to the bus stop or made it to school.

Her parents later discovered that some clothing, a backpack and her bicycle were missing from their home.

Police said there's a chance Jodie went to the Kyneton area, about 40km west of her home.

She was last seen in her school uniform, including a navy-blue raincoat with red stripes and navy-blue tracksuit pants, and had her school bag with her.

Her other bag is a Carlton Football Club backpack with "JODIE B B" printed on it while her bicycle is described as being a metallic blue BMX bike with no mudguards.

Anyone with information on Jodie's whereabouts is asked to call Kyneton police on 5421 2900.

- The Age