Ottawa is under a rainfall warning that Environment Canada says stretches across Eastern Ontario and could bring as much as 50-70 mm of rain within a 24 hour period.
Meteorologist Peter Kimbell says while there will be a lot of rain it will fall steadily.
"Certainly we'll be getting a lot of water. The good news is that it will be fairly spread out over a lengthy period of time and not intense like we saw in Burlington last week. Nevertheless 50 mm in 12-18 hours is still quite a bit of water," said Kimbell.
He said drivers should be cautious of water pooling on the roads, particularly between midnight and 6 a.m.
There is a chance of a thunderstorm and Kimbell warns, "When thunder roars, head indoors."