The province's seven-day rolling average of new cases now stands at 2,862, compared to 2,207 a week ago.
Of Ontario's 34 public health units, 15 logged 30 or more new cases today.
About 22 per cent of schools now have at least one reported case, while 83 schools, or 1.7 per cent of Ontario 4,828 publicly-funded schools, are closed due to COVID-19.
"The rise in severe and critical illnesses is placing renewed strain on the health system and health-care workforce", Dr. Theresa Tam said in a statement. The province's virus-related death toll is now 7,458.
Health Minister Christine Elliott is due to share the number of new diagnoses and vaccinations this morning.More news: Australians are free to travel to New Zealand without quarantine
Meanwhile, 128 new cases were reported in Hamilton, 132 in Niagara and 165 in Ottawa.
Instead, the province introduced a "shutdown" that came into effect first thing Saturday morning.
Ontario also reports 494 patients in intensive care because of COVID-19 and 293 on a ventilator.
The province said 510 patients out of 1,161 hospitalized are now in the ICU with a COVID-19-related critical illness.
More than 300 people are hospitalized, including 96 in the ICU.More news: USA ousts Astra from factory, puts J&J in charge
"The variant is a completely different disease, completely different from classic COVID".
Though this iteration of lockdown is similar to the one we weathered in the winter, there are a few notable differences, including the fact that "non-essential" retail stores can remain open with reduced capacities and that an official stay-at-home order has not been issued.
To date, there have been just over 367,600 cases of the coronavirus and 333,576 recoveries since the first case emerged in the province last January.
More than 890,000 doses of vaccine have been administered so far, 87,000 of which are second doses.
Ontario is expected to reveal two days' worth of COVID-19 statistics today after foregoing yesterday's data drop for Easter Sunday.More news: Jordan’s Prince Hamzah says he is under house arrest
The numbers used in this story are found in the Ontario Ministry of Health's COVID-19 Daily Epidemiologic Summary.