Forty millimetres of rain or more are possible in some parts of southern Ontario, Environment Canada says.

Rain was expected to start moving into southern Ontario Friday afternoon from the west.

Environment Canada warned that rain could fall heavily at times, particularly during the day on Saturday, before tapering off late Saturday.

In some areas, the agency was forecasting between 25 and 40 mm of rainfall.

Huron-Perth, Grey-Bruce and northern parts of Wellington County were expected to escape the heavier amounts of precipitation, although rain was expected to fall steadily in those areas as well.

After the rain moves out, temperatures will cool down, with Waterloo-Wellington’s forecast high for Sunday sitting at 1 C. Early indications suggest some regions could see flurries or heavier snow on Sunday.