Season’s First Snowfall Possible for Wide Swath of Southern Ontario Starting Late Wednesday

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Over the past week, calm conditions have dominated the weather story across Southern Ontario. This pattern has also brought a return to more seasonal temperatures typical for this time of year, a noticeable shift from the unseasonably warm weather that lingered into early November.

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One notable absence so far this season is snow—a staple of November in Southern Ontario. While some regions, especially higher elevations in Central Ontario, the Ottawa Valley, and the Dundalk Highlands, experienced their first flurries as early as September and October, much of Southern Ontario has yet to see its first snowfall.

That, however, could soon change with the arrival of multiple weather systems in the coming days, bringing colder air and the potential for wet flurries as early as Wednesday evening and into Thursday and Friday.

The good news for those not yet ready to embrace winter is that significant accumulation isn’t expected with this initial blast of wintry weather. Temperatures are forecast to hover just above freezing, which will likely limit accumulation as any snow melts upon contact with the wet and relatively warm ground left behind by earlier rainfall.

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In addition to the season’s first flurries, a slow-moving system will stall over the Great Lakes region, pulling in moisture from another system over New England. This setup will lead to ample precipitation, with heavy rain expected to persist into the start of the weekend. Eastern Ontario is poised to bear the brunt of this rainfall, with totals ranging from 25 to 50 mm between Wednesday and Saturday.

SIMULATED RADAR - MAP FROM WEATHERBELL

The rain is expected to begin on Wednesday afternoon, with the initial band of heavy rain arriving in Deep Southwestern Ontario and areas near the Lake Erie shoreline by dinnertime.

This line of precipitation may also bring embedded, non-severe thunderstorms and wind gusts of 70-80 km/h. While most gusts are expected to remain below the severe threshold, isolated gusts near 90 km/h are possible, particularly over the Niagara region during the early evening hours.

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PRECIPITATION TYPE - MAP FROM WEATHERBELL

As this line of rain races across Southwestern Ontario and into the Golden Horseshoe, colder air will begin rushing in from the west. However, there is some disagreement among models regarding how quickly temperatures will drop and how rapidly the precipitation will move. Some projections suggest a sharp cooldown, with temperatures in Southwestern Ontario nearing freezing by Wednesday evening.

If this happens, rain could transition to wet snow in areas such as Sarnia, London, Goderich, Kitchener, Guelph, and Orangeville. However, with earlier rainfall and temperatures still above freezing, any snow is likely to melt on contact. Elevated areas northwest of the GTA, particularly the Dundalk Highlands, may see light accumulation of up to 2-4 cm overnight into Thursday morning.

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PRECIPITATION TYPE - MAP FROM WEATHERBELL

By Thursday morning, most of the moisture will shift into Central and Eastern Ontario, with the centre of the low-pressure system stalled over Lake Huron. Meanwhile, a secondary system over New England will provide additional moisture, enhancing precipitation over Eastern Ontario throughout the day.

Temperatures in parts of Eastern Ontario, particularly southwest of Ottawa and in higher elevations, will hover near the freezing mark, creating a chance for wet flurries. Closer to the international border extending into the Ottawa region, heavy rain will likely continue.

Precipitation is expected to persist overnight Thursday and linger into Friday, with the heaviest rain focused on Eastern Ontario. In Central and Southwestern Ontario, lingering showers are possible Friday morning and afternoon, though they won’t be as intense as in the east.

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For rainfall totals, Eastern Ontario, including Kingston and Ottawa, can expect 25 to 50 mm by Saturday. The rest of Southern Ontario will likely see 10 to 25 mm, though isolated pockets could receive closer to 30-40 mm during thunderstorm activity.

Higher elevations in Eastern Ontario, particularly near Bancroft, may see persistent snow showers that could result in minor accumulation of up to 2-5 cm by Friday morning. However, with temperatures so close to freezing, it’s uncertain how much snow will stick.

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Looking ahead to the weekend, there’s good news for those not ready for snow. Earlier model predictions suggested a significant cooldown that could trigger lake-effect snow. However, the latest data indicates the cooldown won’t be as intense as initially thought.

While some lake-effect showers are still possible along the Lake Huron shoreline and southeast of Georgian Bay on Saturday, it likely won’t be cold enough for those showers to fall as snow.

Temperatures to Soar Above 20°C Across Southern Ontario on Tuesday With Gusty Winds

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As we step into the first days of November, the temperatures outside might have you double-checking the calendar, as the unusually warm trend of this fall continues. This lingering seasonal tug-of-war between cold and warm air has led to temperature swings from near-freezing to over 20°C in the past few weeks.

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Despite the calendar saying November, it’ll feel more like early fall on Tuesday as temperatures rise to around 20°C across much of Southern Ontario. Accompanying this brief warm-up will be strong wind gusts, reaching 70-80 km/h in some areas.

A warm front moving across Southern Ontario is bringing in this surge of mild air, making its presence felt overnight into Tuesday. Already, spots around Lake Erie in southwestern Ontario are feeling this effect, with temperatures climbing near the 20°C mark by Monday evening.

In contrast, parts of Central Ontario and the Ottawa Valley have remained in the single digits, with areas near Ottawa hovering close to freezing. But don’t worry; that’s about to change as warmer air spreads in!

Overnight, temperatures will gradually rise, with most of Southern Ontario waking up to mild conditions in the mid to upper teens. In Central and Eastern Ontario, expect to start the day with temperatures in the lower teens.

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Throughout Tuesday, the warm-up will continue, with daytime highs near 20°C or slightly higher in some areas. The latest data suggests the warmest air will be centred along the Golden Horseshoe and deep southwestern Ontario, including cities like Windsor and Chatham, where temperatures could reach 21-24°C. Some locations may even approach record highs, though with records around 23-25°C in many spots, breaking them might be a tall order.

The rest of Southern Ontario, except for the Bruce Peninsula and northern parts of Central Ontario, will enjoy temperatures around 18-21°C. Northern regions, including Tobermory, Parry Sound, Huntsville, and Algonquin Park, will see slightly cooler temperatures around 15-18°C. Meanwhile, Northeastern Ontario will experience mild conditions, with highs in the low to mid-teens.

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TEMPERATURES 10-14°C ABOVE SEASONAL- MAP FROM WEATHERBELL

If 20°C temperatures in November seem strange, you're right! Daytime highs for this time of year are typically in the upper single digits or low teens, so we’re looking at temperatures around 10-14°C above average across Southern Ontario on Tuesday.

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Winds will also be a key feature on Tuesday, with gusts approaching 70 km/h across much of Southern Ontario by the morning. These winds should weaken somewhat later in the day but are expected to pick up again overnight into early Wednesday.

A few areas—particularly around Lake Erie, Niagara, higher elevations east of Lake Huron, and northeast of Georgian Bay—could see stronger gusts up to 80 km/h, although this will be highly localized. Most places should expect gusts around 70 km/h, with winds easing off by late Wednesday morning.

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Northeastern Ontario will see heavy rain beginning early Tuesday morning and lasting through the day and night, with rainfall totals reaching 30-50 mm by Wednesday afternoon in some spots.

Southwestern Ontario will also see moderate to heavy rain starting early Wednesday morning, which will then spread eastward to the Golden Horseshoe and Eastern Ontario by late morning. However, some models indicate that the rain might weaken before reaching Eastern Ontario, resulting in only a few millimeters. Southwestern and Central Ontario could see rainfall amounts of 5-15 mm.

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Wednesday will bring a dramatic change as a cold front sweeps across Southern Ontario, leading to a significant temperature drop by the day’s end. By Wednesday evening, temperatures across much of Southern Ontario will fall sharply into the low to mid-single digits, giving us a reminder that winter is just around the corner.

Early October Windstorm Will Blow Across the Prairies This Weekend

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The first weekend of October is shaping up to feel like true fall across the Prairies, with a strong low-pressure system bringing powerful wind gusts of 70-100 km/h. These winds are set to begin later this afternoon and continue throughout the day on Saturday. The prolonged high winds will likely strip many trees of their remaining leaves and could pose a serious hazard to traffic, especially for transport trucks and trailers

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The windstorm will kick off in the Alberta Foothills this afternoon, quickly spreading across Southern Alberta as the evening progresses. Expect pockets of gusts exceeding 90 km/h along the QE2 corridor south of Calgary and near the American border. These intense gusts won’t last long in Alberta, though, as the winds are expected to ease overnight.

The storm will move eastward into Saskatchewan through the evening and overnight hours. By morning, the low-pressure centre will stall and the winds will intensify, leading to widespread gusts approaching, and in some areas surpassing, 100 km/h across much of Southern Saskatchewan. These fierce winds will persist into the late afternoon and early evening.

The system will push into Manitoba by late Saturday morning, with strong winds continuing throughout the day before gradually subsiding. The strongest gusts, reaching over 90 km/h, are expected in the southwest corner of the province, but many parts of Southern Manitoba will still experience significant gusts.

Temperatures will cool down a bit following this windstorm, serving as just a taste of the fall storms we can expect as the season progresses.