Santa Claus has ruled out switching to a uniform of shorts, T-shirt and thongs, despite sweating through a tough day at the office on Sunday.

In only his fourth shift as the man in red and white, Peter Richardson's mettle was sorely tested over four hours at City Square as Melbourne's temperature hit a muggy 31.3 degrees at 1.30pm.

While a fellow Santa had an ice skating gig at the O'Brien Group Arena in Docklands, Mr Richardson toughed it out in a shipping container-sized room in the square opposite Melbourne Town Hall.

But he had good coping techniques, such as leaving his padded belly at home, drinking (water) like a fish and cooling off in the square's moat.

Mr Richardson, 63, a retired computer systems administrator, said the Santa suit with fur trim "doesn't give you much in the way of circulation. It's cinched-in with a belt, you've got multiple layers with a cape on the shoulders. It tends to make it reasonably warm."

Tough but fun: Santa hard at work in the heat in the City Square with (left to right) Isabella Meddis, Simae Cutrupi and Patrick Creane. Photo: Simon Schluter

He said it was sweaty work and on future hot days he might ask for a fan.

He's a traditionalist though, and won't be asking to appear in beach wear.

"But if Santas start keeling over from heat stress, maybe they'll have to change it. It's not a good look for Santa to pass out," he said.

The City Square Santa service, open daily until December 24 and funded by the City of Melbourne, is popular because it's free, with Santa's elves using parents' iPhones to take photos.

One boy said he wanted a car. Mr Richardson said he didn't know if that could fit on his sleigh, so they agreed on a toy car. One child wanted to fly and another wanted diamonds.

Cooler Santa: A lucky Father Christmas got a gig ice skating at O'Brien Group Arena in Docklands. Photo: Chris Hopkins

He said the most challenging aspect was kids who screamed at the sight of him.

"I'm sure it's because of the beard. Kids that young are used to seeing a whole face, and when they don't, it scares them."

Mr Richardson said the key was to listen carefully, treat kids as equals and not be condescending.

Referring to the weather, he said, "today was tough. But it's otherwise been a great gig".