High rainfall amounts are expected in the Ottawa region and across much of eastern Ontario, but not enough to trigger a rainfall warning.

Environment Canada says 30 to 40 mm of rain could fall by Thursday morning, with some areas potentially seeing 40 to 50 mm of rain.

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About 20 to 40 mm of rain is expected to fall in the Ottawa region by Thursday morning. (Pawel Dwulit/Canadian Press)

It's due to a large weather system approaching eastern Ontario from the U.S. Midwest.

On Wednesday, the weather agency is expecting a high of 8 C with a 60 per cent chance of rain or drizzle in the morning, and then rain beginning in earnest late in the morning. About 10 mm is expected to fall.

Wednesday night, about 10 to 20 mm of rain is expected with a low of 7 C.

Environment Canada predicts the rain to stop falling on Thursday morning, giving way to cloudy skies, a high of 18 C and a 40 per cent chance of rain. 

The Ottawa forecast then calls for cloudy skies and chances of rain until Tuesday next week.