Environment Canada says Niagara could end up getting anywhere from 30 to 100 millimetres of rain when what's left of Hurricane Sandy hits.

Right now forecasters believe the remnants of the storm will arrive late Monday as a large and powerful post tropical fall storm over Southern Ontario.

Significant rainfall with strong and gusty winds appear likely late Monday into Tuesday.

The storm is expected to weaken later Tuesday and on Halloween, but it will remain cool, damp and may still be somewhat windy for the trick-or-treaters.

The complicating factor is the presence of a stalled front now over Southern Ontario.

Moisture-laden post-tropical storms interacting with fronts can produce significant rainfall.

The front that Niagara has experienced this weekend will bring about 20-30mm of rain when today ends, and stormy Sandy could bring an additional 30-100mm when the storm is over.

Winds will also reach 50 to 70 km/h with strong winds across Southern Ontario beginning late Monday with severe gusts to 100 km/h likely.

Gale to storm force winds are expected on the Great Lakes and St.Lawrence River. 

Environment Canada says the combination of sodden ground, strong winds and some residual leaves on trees will likely lead to areas with power outages due to fallen limbs or downed trees snapping power lines.