Acting Inspector Christine Lalor said William’s family believed he would respond to searchers but “if there were really loud noises or crowds that may deter him”.
Mr Beasley said William is “very calm, just a really calm sort of soul”.
“He loves Thomas the Tank Engine … he loves food. He’s really mobile, I’ve always called him a jungle boy. He loved being outside and running around,” he said.
“He just would have got immersed in being out here and forgotten where he was. As a young fella, you can’t take your eyes off him for long at all. He’s always been fast.”
William was due to return to school in Geelong on Tuesday. He lives mostly with his mother.
Mr Beasley said he was praying for good news on Tuesday and was hoping William had found his way to a home or shelter.
“I can’t even think the other way,” he said.
William was wearing blue trackpants and a hoodie when he disappeared.
Searchers planned to use thermal imaging equipment overnight to find him as temperatures were set to plummet again, Senior Sergeant Greg Paul said.
“This is very dangerous weather, it can get down to zero, perhaps sub-zero, up here in the hills and it is life-threatening weather but we have had people survive several nights in these conditions as well so we are quite serious about trying to find Will as quickly as possible and there is every likelihood we could succeed,” he said.
“I believe it’s going to be getting down to similar [temperatures] as last night, very cold, dangerous. We know we have a time limit on this search.”
He said similar searches in the past, such as that for Luke Shambrook five years ago in which the 11-year-old with autism was found alive after five days near Lake Eildon, gave police hope that William would be found.
The Bureau of Meteorology is expecting temperatures to drop down to 4 degrees overnight at Mount Disappointment, though some valleys could get closer to 1 degree.
Thankfully, no rain is expected until the weekend and frost is less likely for Wednesday morning because of milder conditions.
“We’ll also get a bit of cloud moving over [on Tuesday night] which does tend to restrict the development of frost a little bit,” Mr Delamotte said.
Mostly sunny skies are expected on Wednesday, with light northerly winds and a maximum temperature of about 10 degrees at the summit. Nearby valleys could be closer to 13 or 14 degrees.
“That’s probably a touch warmer than what we saw [on Tuesday] through that area,” Mr Delamotte said.
Acting Inspector Lalor urged anyone who had not yet checked their homes, out-houses or sheds – even if they live further afield – to do so as soon as possible, as the teen may be hiding.
“He is quite active so looking at the time now, he could have travelled quite a distance,” she said
There were no reported sightings of William on Tuesday.
“The longer it goes on, the more concerned we are,” she said.
Acting Inspector Lalor said William’s family, who were at the search site on Tuesday, were “quite distraught”.
“It’s pretty devastating for anyone missing a child, but they are holding up as well as they can,” she said.
Searchers on Tuesday entered the bush on foot, motorbikes and on horseback, calling out “Will” as they made their way through the thick undergrowth. Police dog Ollie also scoured the trails for the teen.
Local man Mark, who did not want his surname published, decided to join the search after hearing the news overnight.
“I used to work in forestry and helped to build the walking tracks to the summit,” he said. “I know all these tracks quite well so I thought I could be of some use.”
It would be “very, very easy” to get lost in the dense bush, he said.
“It’s as rugged bushland as anywhere in Victoria. Fortunately, it’s not huge, but it’s thick and hard to see because it’s fire regrowth.”
William taps his chest and makes noises to communicate. He understands verbal communication, but does not like loud noises or to be touched. Police are advising anyone who approaches him to do so calmly and quietly and call triple zero.
Much of Tuesday’s search was concentrated around the summit of the mountain.
with Rachel Eddie
Simone is a crime reporter for The Age. Most recently she covered breaking news for The Age, and before that for The Australian in Melbourne.
Paul is a reporter for The Age.