The stricter public health measures come into effect in Hamilton, York, and Halton regions.
Toronto joined Peel Region in the red alert level—the highest short of a full lockdown—on Saturday.
Another six regions, such as Durham and Waterloo, will move to the orange alert level, and six more, including Windsor-Essex and Sudbury, will join the yellow alert level.
Today’s developments come just days after Premier Doug Ford lowered the thresholds for his colour-coded restrictions system.
He said on Friday that recent COVID-19 projections show the province is “staring down the barrel of another lockdown.”