Dave and Jill Pelvin say their 1-year-old son, Greyson, was playing with his two other siblings and friends in a splash park in Georgetown, a community in Halton Hills, on Monday when he stepped on the grate and suffered second-degree burns. The boy also suffered a minor burn to his right hands in the process.
Greyson was raced to hospital and remains at Toronto's SickKids hospital on Monday.
Both of the boy's parents are distraught about the incident.
"I don't know when the nightmares stop ... things could have gone so differently yesterday," said Jill Pelvin.
"It is so easy for it to happen. Anyone who steps on it will get serious burns," Dave Pelvin said, adding many would have no idea how dangerous similar grates can be.
Dave Pelvin posted an image of his son's injuries on Facebook as a warning to other parents. He said since Greyson's injury, a friend told him park staff have barricaded the grate.
Greyson, meanwhile, is still being treated with pain-killers at SickKids Hospital. Specialists are set to re-examine his injuries tomorrow to see if he will require a skin graft to repair the soles of his feet, his family said.