Southern Ontario is in the middle of an unusually long dry spell, thanks to a powerful ridge of high pressure that has been strong enough to set September records across Eastern Canada.

According to The Weather Network, the system set all-time September pressure marks in Montreal, Quebec City, Chibougamau and Val-d'Or, Que., as well as in Ottawa.

Records fall as pressure soars

Readings Wednesday morning included 1041 mb in Saguenay, 1036.9 mb in Quebec City, 1039.2 mb in Chibougamau, 1037.4 mb in Montreal and 1037.5 mb in Val-d'Or. Ottawa's barometric pressure climbed to 1037.4 mb.

All of those marks were records, and each one towers over the standard sea-level pressure of 1013 mb.

Dry streak building at Pearson

The same weather pattern is extending a notable stretch of rain-free days in the Greater Toronto Area. Toronto Pearson International Airport had gone six consecutive days without rainfall as of Wednesday, according to The Weather Network.

That puts the current streak close to breaking Pearson's longest dry spell of 2026, which ran seven days from May 29 to June 4.

The next legitimate chance for rain is not expected until Sept. 30 and into Oct. 1. If the forecast holds, the current dry stretch could stretch to about 12 days — surpassing even a memorable dry run last year that lasted 11 days, from Sept. 26 to Oct. 6.

Pearson has recorded just 48.1 mm of rain so far this month, and most of it fell on a single day, when 43.3 mm was reported on Sept. 2. The airport's normal monthly rainfall is 69.4 mm.

Why the rain is staying away

A strong upper-level ridge remains anchored over the region, with the high-pressure system over Quebec forecast to stay near 1040 hPa and dominate Eastern Canada.

The blocking pattern splits the jet stream, pushing the northern branch upward and steering the southern track away — effectively isolating Ontario and Quebec from active storm systems.

Sinking air beneath the high is limiting cloud growth and choking off any chance of showers, while lighter winds are expected over the next few days.

More sunshine ahead

For GTA residents, that translates into a string of bright autumn days. Sunny, dry conditions are expected to persist Thursday and Friday, with highs around 18 C and 20 C respectively, and daytime readings warming to about 22 C as the week ends.

The ridge is forecast to slowly weaken and drift heading into the weekend, but the persistent block should continue to keep major weather disturbances away from the region, leaving little opportunity for meaningful rainfall in the near-term forecast.

While the high pressure has brought stable weather, The Weather Network cautions that September can still bring surprises, and residents should stay on top of any changes in the forecast.