Significant Precipitation and Temperature Drop Expected Across Canada and the United States

Affected by the eastward movement of a cold vortex (Figure 1), moderate to heavy rain, with localized downpours, is expected from today through the 6th in southern and eastern Canada, as well as northeastern United States. Higher elevations will experience light to moderate snow or sleet. The cumulative precipitation during this period is anticipated to reach 40-80 mm, with localized areas exceeding 110 mm (Figure 2).

The aforementioned regions will also experience a temperature drop of 6-10 ℃, with localized areas potentially seeing a decrease of more than 12 ℃ (the average temperature will be significantly lower than the same period in previous years by over 6 ℃, Figure 3). Additionally, winds of 5-6 on the Beaufort scale are expected, with gusts exceeding 8 levels. Precautions should be taken to mitigate the adverse effects of the heavy rainfall and cooling weather on transportation, as well as on daily life and production activities.

Figure 1  500 hPa Geopotential Height (Isopleths) and 850 hPa Wind Field (Wind Barbs) at 12:00 UTC on September 5, 2025

Figure 2  Forecasted Accumulated Precipitation from September 3 to September 7, 2025, 00:00 UTC (Units: mm)

Figure 3  48-hour Cooling Forecast at 12:00 UTC on September 4, 2025 (Unit: °C)

Author: Hu Yingying                                 Reviewer: Ma Jie 

English reviewer:Wang Yi                                                                       Issue approver:Dai Kan