Rain and warmth creates ideal flood setup in southwestern Ontario

The beginning of April was marked by severe thunderstorms, mild temperatures, gusty winds and rainfall in parts of southern Ontario, resulting in localized flooding in some areas

Mother Nature wasted no time in bringing stormy weather to Ontario, with wintry conditions in the north, and thunderstorms, flooding and mild temperatures in the southern sections.

After some pre-dawn rumbles, the threat for thunderstorms returned to southern Ontario Saturday afternoon. The first round early Saturday brought locally heavy rainfall of up to 40 mm, with up to an additional 30 mm expected in the afternoon, contributing to further overland and river flooding.

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Hamilton, Ont. flooding/Matt Di Nicolantonio

(Matthew Di Nicolantonio/The Weather Network)

Localized flooding was observed in Hamilton and in West Montrose, just west-northwest of Guelph. The Grand River watershed is also currently experiencing flood-warning criteria. With Saturday's above-seasonal temperatures, along with the risk of thunderstorms and rainfall, the chance of more localized flooding occurring in southwestern Ontario is highly elevated.

Saturated grounds in southern Ontario means runoff will happen quickly as the storms move through Saturday. This has raised some river levels, as well, so people should avoid all waterways.

Severe thunderstorm warnings and watches were issued for some areas.

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A steady, drenching rainfall amounts of 20-30 mm are possible along the Lake Erie shores and Niagara region. Higher amounts are possible in thunderstorms.


Gusty winds will also accompany the rain and warmer temperatures, so localized power outages and tree damage is possible.

Rainfall will ease into Sunday with a sharp temperature plunge, but waterways will remain elevated so the flood danger will likely persist throughout the weekend.

With some of the severe thunderstorms, there's been reports of pea-sized hail and downed hydro poles in parts of the region.