A sudden stratospheric warming event has begun, deforming the Polar Vortex and setting the stage for a colder start to winter across the United States, Canada, and Europe.
An early stratospheric warming developing over the Arctic in late November 2025 is raising the likelihood of colder conditions and increased snowfall across parts of the United States, Canada, and possibly Europe in December.
A record-breaking bomb cyclone ripped through Newfoundland from November 4 through 5, 2025 bringing along Category 2 hurricane force winds, coastal flooding, and causing widespread damage across the region.
Forecast data indicate an early weakening and displacement of the stratospheric polar vortex over the Arctic in October 2025, as a developing high-pressure anomaly over Greenland interacts with the circulation earlier than usual, increasing the chances of colder air movement toward the mid-latitudes of North America and Europe.
A strong atmospheric river is forecast to shift southward along the British Columbia coast between September 26 and 29, 2025, bringing several low-pressure systems and periods of heavy rainfall to Vancouver Island and the South Coast. Forecasts suggest up to 100 mm (4 inches) of rain in west-facing coastal mountains, with persistent showers likely across the Lower Mainland.
A severe hailstorm struck southeastern Alberta, Canada, on August 20, 2025, producing wind gusts up to 150 km/h (93 mph), large hail, and widespread damage to crops, livestock, and infrastructure.
Toronto, Ontario recorded one of its hottest summers on record in 2025, with six heatwaves, 14 days above 32°C (90°F), and 24 nights above 20°C (68°F) as of August 24, according to Environment Canada.
An atmospheric river (AR) with moderate-to-strong integrated vapor transport (IVT) exceeding 500 kg m⁻¹ s⁻¹ is forecast to make landfall over the Pacific Northwest and southern British Columbia on the evening of August 14, 2025, bringing sustained AR conditions for about 24 hours and significant precipitation through August 16.
The first significant rainfall event in weeks is forecast for coastal British Columbia, Canada, with an atmospheric river expected to bring 20–40 mm (0.8–1.6 inches) to the Lower Mainland and over 50 mm (2 inches) to higher elevations from August 15 to 17, 2025. The rainfall is expected to bring some relief to the region following prolonged wildfire activity that has scorched over 7 000 000 ha (1.8 million acres) across Canada making it the country’s second-worst wildfire season on record.
Severe thunderstorms impacted eastern Ontario and southern Quebec, Canada on July 13, 2025, producing up to 100 mm (3.9 inches) of rain in 90 minutes, flash floods, wind gusts up to 90 km/h (56 mph), and widespread power outages affecting more than 60 000 customers.
