Heavy Rain Aimed At Ontario; 20-60mm Expected

We are closely watching a system currently over the United States as it moves into Southern and Northeastern Ontario. The system is expected to bring widespread rainfall totals between 20 and 40mm with local totals towards 60mm.

Beginning this evening, showers will move into Northwestern and North Central Ontario. The showers may mix with snow at times along the northern shores of Lake Superior. Into the morning hours (4-8am), showers and thunderstorms will cross Lake Huron and move into Southwestern/Northeastern Ontario near the Bruce Peninsula and Manitoulin Island. Showers mixing with snow will affect portions of Northwestern and Northeastern Ontario. At times near Timmins, Cochrane extending towards Hearst, the snow may be moderate to heavy. Into the mid-morning hours (8am-12pm), scattered showers and non-severe thunderstorms will be likely across Southwestern Ontario into the GTA, Extreme South and extending into Central Ontario. The thunderstorms may extend into Northeastern Ontario. Scattered showers will be likely across portions of Northeastern Ontario with a mix of rain and snow for the northern portions of this region including Northwestern Ontario. Into the afternoon (12-4pm), scattered showers and local thunderstorms may be possible in Northeastern Ontario with scattered rain and snow from Marathon and Timmins towards the north. In Southern Ontario, scattered developing thunderstorms, mainly non-severe are likely across Southwestern Ontario. We are expecting mainly non-severe thunderstorm although, a very isolated severe thunderstorm can't be ruled out. Into the evening hours (6-9pm), scattered pockets of rain are possible in Northeastern Ontario with moderate to heavy rain in Central and Eastern Ontario. Mainly non-severe thunderstorms will be possible across the GTA and Golden Horseshoe region including portions of Central and Eastern Ontario. Into the early morning hours on Friday, moderate to heavy showers and thunderstorms are possible in Eastern Ontario with some isolated thunderstorms possible in the Extreme South. Besides this, light, scattered showers are possible in Northeastern Ontario. Into the morning hours on Friday, isolated thunderstorms may cross from Central to Eastern Ontario and into Quebec alongside the scattered, light rain and cloud-cover over the region.


Across Northern Ontario, a widespread swath of 5 to 10cm is likely from the Thunder Bay/Nipigon Area across the northern shores of Lake Superior to include Hearst, Timmins, Cochrane and Peterbell. Local amounts may reach 15cm although this is unlikely. Further south towards Wawa, Chapleau and Temiskaming Shores, local totals near 5cm of snow may be possible.


Across Southern Ontario on Wednesday Night into Thursday Morning, widespread 60-80km/h wind gusts are likely to develop across Southern Ontario including portions of Northeastern Ontario. For areas east of Lake Huron such as Huron, Perth, Grey, Bruce and Wellington Counties, including the shores of Georgian Bay such as Manitoulin Island extending inland towards Espanola, Sudbury and North Bay including Huntsville, Parry Sound and Algonquin Park, wind gusts may be enhanced towards 70-90km/h.

Severe Thunderstorms

As mention in the timeline post, there is a low risk for severe thunderstorms tomorrow afternoon. Following the morning thunderstorms, there is a possible period of clearing which may develop across portions of Southwestern Ontario. In the case of this happening, instability may build and isolated thunderstorms may develop, as stated in the timeline listed above. These thunderstorms could be locally severe at times with gusty winds, heavy rain and even small hail. These storms are likely to weaken once entering the GTA and Central Ontario although, there is a small area near Niagara and possibly near Oshawa which may see the local severe risk continue.

If the conditions warrant a severe thunderstorm forecast map, one will be posted as a separate post tomorrow (Thursday) afternoon and will be linked in this post. This post will also be visit able on all social media, the website and all previously-known websites.


Rainfall Forecast, for Southern Ontario. Issued May 8th, 2019.

Blue or '1':

Areas in the blue or marked with a '1' can expect less than 10mm of rain. This includes much of Northern Ontario for areas including and north of Shebandowan, Nipigon, Manitouwadge, and Matheson.

Green or '2':

Areas in the green or marked with a '2' can expect between 10 and 30mm of rain. This includes portions of Northern Ontario in a thin band including and between Cloud Bay, Thunder Bay, Marathon, White River, Timmins and Temiskaming Shores. Most of this region should see totals less than 20mm although local totals around Cloud Bay as well as near Nicholson, White River, and Temiskaming Shores may reach between 20 and 30mm of rain. Local totals towards 40mm can be ruled out in this region. This region is along a transition line between snow and rain, therefore, totals may be limited if snow is more predominant. In Southern Ontario, a widespread 20 to 30mm can be expected across Southwestern Ontario extending south and west of Owen Sound, Angus, Vaughan, and Toronto. This also includes Huron, Perth, Wellington, Middlesex, Lambton, Norfolk, Haldimand, and Essex Counties including the region of Halton, Peel, Niagara, Chatham-Kent, and Waterloo. The cities of Hamilton and Toronto also are included in this region. Local patches towards 40 and even 50mm may be possible over the Delhi-Hamilton-Niagara region. Thunderstorms may enhance rainfall totals across the whole region.

Yellow or '3':

Areas in the yellow or marked with a '3' can expect between 20 and 40mm of rain. This includes portions of Northern Ontario in a thin band including and between Wawa, Chapleau. Ruel, Temagami, Sault Ste. Marie and Agawa Bay. Most of this region should see totals between 20 and 30mm although local totals from Wawa inland towards Sultan and south towards Ranger Lake, including Sault Ste. Marie and everything in between may see those totals towards 40mm. Towards the north such as Wawa and Chapleau, rainfall totals may be lower due to snowfall being a more predominant precipitation type. In Southern Ontario, a widespread 20 to 30mm can be expected near the border of the United States. This includes Cornwall, Brockville, Kingston, Belleville, Perth, Peterborough, and Oshawa. Further north, this includes Barrie, Orillia, and Midland as well as Wiarton. Most places will see between 20 and 30mm although totals between Oshawa, Peterborough and Belleville may be locally higher towards 40 and 50mm and totals near Alexandria and Maxville may see locally fewer totals at or near 20mm. Thunderstorms may enhance rainfall totals across the whole region.

Orange or '4':

Areas in the orange or marked with a '4' can expect between 25 and 50mm of rain. In Northern Ontario, this includes everything south of Thessalon, Elliot Lake, Sudbury, and Temagami. In Southern Ontario, this includes everything north of Lion's Head, Washago, Fenelon Falls, Sharbot Lake, Ottawa, and Hawkesbury. Everywhere between this Southern-Northern Ontario regional list are also included in this area. This includes Algonquin, Manitoulin, Britt, Bancroft, Haliburton and Parry Sound. Most places throughout the region will see between 25 and 35mm. Totals from Tobermory and Manitoulin Island eastward through Britt, Algonquin, and North Bay, rainfall totals may reach towards 50mm with local totals as high as 60 or even 70mm. In Eastern Ontario near Ottawa, Hawkesbury and Arnprior, rainfall totals at or near 25mm are likely. Among the widespread 25 to 35mm, pockets of 35 to 50mm are likely throughout the region. Thunderstorms may enhance rainfall totals across the whole region.

*Disclaimer: the rainfall risk will be heaviest dependable on how many thunderstorms, if any, move through a region and the exact track of the system. Amounts may vary.


Rainfall Forecast, for Northern Ontario. Issued May 8th, 2019.



The Ministry of Natural Resources and Forestry have issued a FLOOD WATCH for Southern and Northeastern Ontario.

Flood Alerts | May 8th, 2019 | Northern Ontario | Ministry of Natural Resources and Forestry

Flood Alerts | May 8th, 2019 | Southern Ontario | Ministry of Natural Resources and Forestry

Multiple local conservation areas have issued FLOOD WATCHES (brown) and FLOOD WARNINGS (red).

The Ministry of Natural Resources and Forestry including the MOST up-to-date flooding information can be found on their website: here.

There are still remaining road closures from the improving floods in Central and Eastern Ontario. Sadly, these further rains will likely prevent the situation from getting better.

There are still a few municipalities across Central and Eastern Ontario who have declared a state of emergency.

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