The Grand River Conservation Authority has issued a flood warning for parts of the Nith and Speed rivers as a swell of heavy rain that hit Waterloo Region on Monday night.

The region is expected to get 25 millimetres of rainfall between Monday evening and Tuesday morning. That rain "will cause flooding across portions of the Grand River watershed on Tuesday," the authority said in a release.

The authority has also issued a flood watch, an advisory that indicates a less severe risk of flooding than a warning, for the Grand and Conestogo rivers.

The flooding could extend until the weekend as temperatures rise into the low teens by Thursday, the authority said. That could melt the snow pack in the upper watershed, causing more flooding.