Toronto Weather: Significant Rainfall and Freezing Rain Trend Summary

TL;DR

• Environment Canada warns of heavy rain and freezing rain across Southern Ontario.
• Toronto and Hamilton may see up to 50 mm of total rainfall by Wednesday.
• Flash flood risks and icy road conditions are expected to impact the morning and evening commutes.
• Freezing rain in Ottawa and Eastern Ontario could last for several hours.

What Happened

On Monday, March 9, 2026, meteorologists identified two distinct low-pressure systems moving toward the Great Lakes region. The first system began moving into Southern Ontario Monday night, bringing an initial wave of precipitation. Environment Canada quickly escalated advisories to special weather statements for Toronto, Hamilton, London, and the Waterloo Region. By Tuesday morning, the transition from mixed precipitation to steady rain began as temperatures hovered near the freezing mark, creating hazardous slick surfaces on secondary roads and sidewalks.

Key Developments

Forecasters are tracking a significant rainfall event for the Greater Toronto Area (GTA), with accumulation estimates ranging between 30 mm and 50 mm. In Hamilton and London, officials have warned of "heavy downpours" that could lead to localized flash flooding in low-lying areas. Further east, in Ottawa and the surrounding valley, the primary concern is prolonged freezing rain. Authorities there are warning of several hours of ice buildup on power lines and trees. Environment Canada noted that while the ground remains partially frozen, the soil's ability to absorb water is limited, increasing the volume of runoff into sewers and local waterways.

Why This Matters

The combination of high rainfall totals and frozen ground significantly increases the risk of flooding. For the GTA, this could result in water pooling on major highways like the 401 and DVP, creating dangerous hydroplaning conditions. In regions facing freezing rain, the weight of ice accumulation poses a direct threat to the electrical grid, potentially leading to localized power outages. These back-to-back storms mark a volatile transition in the March weather pattern, shifting from typical winter conditions to high-moisture spring systems.

What Happens Next

The heaviest rainfall is expected to persist through late Tuesday night and into Wednesday morning. Residents in flood-prone areas should monitor local conservation authority alerts for rising water levels. In Ottawa, crews are on standby for potential power restorations as the freezing rain is predicted to taper off by Wednesday afternoon. Temperatures are forecast to stabilize above freezing by Thursday, which should assist in the melting of any residual ice buildup.

Key Terms & Concepts

Flash Flood

A rapid flooding of low-lying areas caused by intense rainfall over a short period of time.

Freezing Rain

Rain that falls as a liquid but freezes upon contact with the ground or other cold surfaces, forming a coating of ice.

Special Weather Statement

An official notification issued by Environment Canada to advise the public of unusual or potentially hazardous weather conditions.

Frequently Asked Questions

How much rain is expected in Toronto?
Toronto is forecast to receive between 30 mm and 50 mm of rain through Wednesday, March 11, according to Environment Canada.

Is there a risk of power outages?
Yes, particularly in Ottawa and Eastern Ontario where prolonged freezing rain on March 10 could cause ice to build up on power lines.

Will the rain cause flooding in Southern Ontario?
Authorities have warned of a flash-flood risk because the partially frozen ground cannot absorb the heavy rainfall, leading to rapid runoff.

When will the freezing rain start in Ottawa?
The freezing rain system is expected to impact the Ottawa region starting late Monday night and continuing through much of Tuesday.

Are travel conditions affected?
Travel is expected to be difficult across Southern Ontario due to heavy rain, reduced visibility, and icy patches on roads through mid-week.