Durham Fall Weather 2026 could begin with cooler temperatures and above-normal rainfall in September, according to the latest long-range outlook from the Old Farmer’s Almanac.
The prediction applies across southern Ontario, including Oshawa, Whitby, Ajax, Pickering, Clarington, Uxbridge, Scugog and Brock.
The almanac expects September to average approximately 15 C, about one degree below normal. Total rainfall could reach roughly 115 millimetres, which would be about 25 millimetres above the region’s seasonal average.
Cooler September predicted
The first half of September is expected to alternate between sunshine, showers and warmer periods.
The almanac predicts cool weather from September 1 to 4, with sunnier conditions in eastern areas and more rain farther west.
Warmer conditions and thunderstorms could follow between September 5 and 8.
From September 9 to 16, showers are expected in eastern southern Ontario, while western areas may experience sunnier conditions. Temperatures are predicted to remain cooler overall.
Another period of showers could arrive between September 17 and 23 before sunnier and cooler weather returns.
The final week of September is expected to become rainy and chilly.
Rainfall could remain above normal
The Durham Fall Weather 2026 outlook suggests residents should be prepared for more frequent rain during the first part of autumn.
The Old Farmer’s Almanac predicts precipitation will be above average across much of Canada, with rainfall potentially well above normal in eastern parts of southern Ontario.
A wetter September could affect outdoor events, construction, farming, road conditions and the timing of fall yard work.
Drivers should be prepared for wet leaves, reduced visibility and water collecting on roadways during heavier rain.
Residents planning festivals, sports events or other outdoor activities should continue checking short-range forecasts closer to each date.
October may remain cool
The almanac expects temperatures to remain below normal in October before moving closer to seasonal averages later in the month.
Rainfall is also predicted to remain above normal through much of the fall season.
However, long-range seasonal forecasts cannot determine the exact timing of individual storms, cold fronts or periods of warm weather.
Short-term Environment Canada forecasts will provide more reliable information about specific days as autumn approaches.
El Niño could influence later weather
A developing El Niño pattern may affect Canadian weather later in 2026.
El Niño occurs when surface waters in the central and eastern tropical Pacific Ocean become warmer than normal, changing atmospheric circulation and weather patterns around the world.
Recent international climate outlooks indicate that El Niño conditions are strengthening and could influence global temperature and rainfall patterns during the August-to-October period.
However, its strongest and most predictable effects in Canada are generally felt during winter rather than early fall.
Weather experts have cautioned that it remains too early to determine precisely how the developing pattern will affect individual Ontario communities.
Long-range forecasts should be treated cautiously
The Old Farmer’s Almanac bases its forecasts on historical weather patterns, solar activity and long-term statistical methods.
Its predictions can provide a broad seasonal outlook, but they should not be treated as guaranteed daily forecasts.
Actual rainfall and temperatures in Durham Region will vary depending on storm tracks, lake influences and local conditions.
Residents should use the seasonal outlook as general planning guidance and rely on Environment Canada for official watches, warnings and short-term forecasts.
Preparing for a wet fall
If the Durham Fall Weather 2026 prediction proves accurate, residents may want to inspect eavestroughs, downspouts, storm drains and basement drainage systems before September.
Property owners should also clear leaves and debris from drainage areas and ensure outdoor furniture and equipment can withstand repeated rain.
The forecast suggests Durham Region may experience an early taste of fall during the final week of September, with cooler temperatures and persistent rainfall bringing a noticeable change from summer conditions.
