A yellow-level rainfall warning is in effect for Waterloo region, Guelph and Wellington County with Environment and Climate Change Canada saying between 20 to 40 mm of rain is possible Saturday during the day and overnight into Sunday.

“A Colorado low will bring rain to the area today and tonight. The heaviest rain is expected to fall this evening and tonight, with locally higher amounts possible in thunderstorms,” the warning on the website on Saturday said.

“The ground may have little ability to absorb further moisture due to recent rainfall events.”

The warning noted people should be aware of water pooling on roads and possible flooding in low-lying areas.

“Watch for washouts near rivers, creeks and culverts,” the warning said.

With heavy rain, visibility may be suddenly reduced at times.

For people travelling outside the region, rainfall warnings were also in effect for much of southern Ontario including in Toronto, London, Muskoka, Huron County and Collingwood.

Flooding possible, GRCA warns

On Friday, the Grand River Conservation Authority (GRCA) terminated all flood warnings but said the entire watershed remains under a flood watch.

The watershed includes communities like Grand Valley, Drayton, Waterloo region, Guelph, Wellington County, Brant County, Brantford, Six Nations and Haldimand County.

“Water levels and flows are gradually declining but remain above normal following the heavy rainfall earlier this week,” the GRCA said in its flood watch statement.

“Some localized flooding of low-lying areas may still be occurring due to elevated levels; however, rivers are no longer exceeding levels associated with significant flooding.”

More rainfall could result in “significant runoff” and lead to rising water levels again, the authority noted.