Ontario reported 2,453 new cases of COVID-19, the highest single-day total in more than two months.
The province also reported 16 more deaths.
New daily cases include 814 in Toronto, 411 in Peel Region, 263 in York Region, 156 in Hamilton, 139 in Durham and 115 in Ottawa, according to Health Minister Christine Elliott.
Saturday's daily case count comes before the province moves two regions into more restricted areas of its colour-coded reopening framework on Monday. As well, five regions in the province's grey lockdown zone will see some restrictions loosen on Monday and later in April.
Meanwhile, the daily case count is the highest since 2,662 cases of COVID-19 were recorded on Jan. 22.
Saturday's total marks the third straight day that the daily case count has topped 2,000.
The new cases come as the province's network of labs completed 61,005 tests for SARS-CoV-2, the virus that causes COVID-19, and registered a test positivity of 4.5 per cent, an increase from 3.8 per cent on Friday.
The seven-day rolling average of daily cases across the province rose to 1,944, an increase from 1,855 on Friday. The average has increased every day for the last 12 days.
The health ministry reported 985 people in hospitals across the province with the virus. This total marks the highest number of hospitalizations since Feb 6., when the province reported 1,021 people in hospital.
Public health units recorded another 16 new deaths on Saturday, bringing Ontario's cumulative total of virus-related deaths since the pandemic began to 7,308.
Ontario reported that 77,740 doses of a COVID-19 vaccine were administered since the last daily update. A total of 1,916,332 vaccines have been given in the province so far.
The province says 308,301 people have been fully vaccinated.
Hospital CEO calls for new measures as case numbers rise
One hospital president is speaking out about the rise in numbers on Saturday.
Eric Vandewall, president and CEO of Joseph Brant Hospital in Burlington, said on Saturday that critical care occupancy will hit the highest ever number this weekend as the variants of concern become the majority.
Dr. Barbara Yaffe, the province's associate medical officer of health, said variants of concern are driving up case counts and admissions to hospitals and critical care.
"Daily cases are increasing, hospitalizations are increasing and ICU admissions are increasing," Yaffe told reporters on Thursday. "As [variants] take over to be the predominant strains, the concern is that the infection rate will increase."
According to Saturday's numbers, Ontario is reporting another 931 cases that have screened positive for a mutation that indicates the presence of a variant of concern. A total of 17,611 cases have now screened positive for the mutation.
A genetic sequencing process is required to pinpoint which variant of concern is present in a sample.
Ontario's COVID-19 science advisory table says variants of concern currently account for about 55 per cent of all new infections in the province.
One government agency that tracks hospitalizations and admissions to intensive care units is also flagging that the province's ICU capacity is reaching a critical level.
The Ontario Hospital Association said the number of severely ill patients is approaching a previous peak. On Friday, it said 401 people with COVID-19 were in intensive care units across Ontario and the number may yet surpass an earlier record of 420 people.
Rules tighten in some areas, loosen in others on Monday
Starting on Monday at 12:01 a.m., Hamilton will move into the grey-lockdown zone, while the Eastern Ontario Health Unit will move into the red-control zone.
The province announced the tightening of restrictions for these two regions on Friday, citing "concerning trends in key health indicators" in some regions, according to Elliott.
Also on Monday, the province will allow outdoor fitness classes, outdoor training for team and individual sports and outdoor personal training in grey-lockdown zones, but these activities will be limited to a maximum of 10 patrons with physical distancing and screening measures in place.
And as of April 12, some personal care services in grey-lockdown zones will be allowed to open at limited capacity by appointment only. These services include hair and nail salons, barber shops and body art establishments.
Regions currently in grey-lockdown include Toronto, Peel Region, Lambton, Sudbury and District, and Thunder Bay District.
Starting on Monday in all levels of its framework, the province will adjust capacity limits for services such as weddings and funerals to ensure more people can gather so long as they can maintain two metres of physical distance. The province did not specify what those capacity limits will be.
Toronto residents aged 70+ can book COVID-19 vaccines
Toronto residents aged 70 and older can start booking COVID-19 vaccinations at city clinics on Saturday.
Mayor John Tory announced on Friday that the city was expanding the eligibility to the age group, urging people to get the vaccine.
Tory said the number of elderly residents signing up for the shot has been decreasing since March 22, when bookings opened to those aged 75 and older.
He said the city has almost 30,000 appointments available over the coming week.
Starting on Saturday, individuals born in 1951 and earlier can schedule their shots through the province's booking portal.
On Saturday morning, Tory tweeted that over 4,300 people had booked a COVID-19 vaccine appointment at a city clinic in the first hour that registration was open to the 70-plus age group.
The city said appointments will be available at three of Toronto's mass immunization clinics on Saturday and at two additional clinics as of Monday
To date, Toronto Public Health says 453,932 COVID-19 vaccine doses have been administered in the city.