Barometric Pressure Forecast for Markham, Canada
Barometric pressure forecast for Markham, Canada — on the south slope of the Oak Ridges Moraine north of Toronto, where Lake Huron snow squalls and Colorado lows both reach. See current barometric pressure and what it means for weather-sensitive people.
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Pressure and weather in Markham
Markham occupies gently rising ground in York Region, between the Lake Ontario shore plain to the south and the sandy hills of the Oak Ridges Moraine to the north, high enough above the lake that it regularly holds snow when downtown Toronto is seeing rain. Two very different mechanisms drive its weather. The first is the organised low-pressure system: Colorado and Texas lows lifting northeast toward the lower Great Lakes bring the region's largest snowfalls and its deepest, slowest declines in barometric pressure, often over a day and a half, while faster Alberta clippers cut across with shallower minima and lighter snow. The second is lake effect, which in the Greater Toronto Area typically arrives not from Lake Ontario but from Georgian Bay and Lake Huron to the northwest, in the form of long snow squall bands that travel southeast across the moraine on a strong northwesterly flow behind a cold front. Those squalls produce whiteout conditions with almost no accompanying pressure signal, since the barometer has usually already risen behind the front. Spring and early summer add lake-breeze fronts off Lake Ontario, which often stall near the moraine and trigger afternoon thunderstorms. Late summer under a ridge is the flattest part of the year. A barometric pressure forecast for Markham is most useful from November through March.
What this means for you
Can barometric pressure cause headaches? Around Toronto the heaviest snow days and the biggest pressure changes are often not the same days, because squall events happen under rising pressure. Keeping a log in Pressure Pal as a migraine tracker app helps you tell whether it is the storm system or the cold outbreak behind it that matters for you. Check current barometric pressure when a Colorado low is being tracked.