More rain, foggy conditions in Toronto’s forecast on Thursday - CP24

Why fall mornings bring fog, frost, and a riskier commuteFall's first cold morning can trigger a chain reaction before you even leave the driveway: Frost coats the windshield, the tire pressure lights up on your dash and fog hides the road ahead. The weather setup starts overnightFall's longer nights give the ground more time to release the heat it absorbed during the day. Clear skies let that heat escape more efficiently, while light winds keep warmer air above from mixing back down to the surface. High pressure often sets up these exact conditions — clear and calm.(MORE: Weather alerts decoded: What advisories, watches and warnings really mean) This process is known as radiational cooling, and it steadily lowers the temperature of the ground and the air just above it.

Toronto and Montreal have remained above the freezing mark every day for almost six months. While frosts and even some snowflakes have intruded across parts of Ontario and Quebec in recent weeks, the two cities have yet to reach that magic number. What’s even more remarkable is that a handful of communities across the southern United States have already dipped to the freezing point--and some have even seen accumulating snowfall. DON’T MISS: Official: Canada records first -30°C reading of the seasonThe last time we saw a freezing temperature in either Toronto or Montreal was the second-to-last week of April. Toronto hit -1.3°C early on April 20, while Montreal dipped to -2.0°C the following morning. Our average first frost in both cities occurs right around the middle of October. But warmer-than-normal years can see this milestone slide several weeks past due. Montreal once had to wait 207 consecutive days for its first frost, with the city’s first subfreezing temperature in 2017 waiting until Nov. 7. The latest Toronto’s had to wait to hit the zero-degree mark was Nov. 13, 2022.

Tropical cyclones top the list of nature’s most powerful storms. Larger than tornadoes and more intense than any single thunderstorm, these systems can change the landscape when they swirl ashore. A handful of tropical cyclones take full advantage of their surroundings to achieve the apex of their potential, the strongest storms nature can produce. DON’T MISS: What’s the difference between hurricanes, typhoons, and cyclones? Tiny fraction of storms achieve upper limitsOnly about 4 per cent of all the world’s recorded tropical cyclones have reached the equivalent of Category 5 strength. Most tropical cyclones are relatively weak and short lived because it’s tough for all the necessary ingredients to align just right. But explosive development can result when all those factors come together in perfect harmony. Strongest Winds: Hurricane PatriciaAn exceptionally favourable setup off the western shores of Mexico in late-Oct. 2015 allowed Hurricane Patricia to grow into the world’s strongest hurricane since reliable observations began in 1966.

While there have been some weather hiccups in October across Canada, one commonality is the lack of fall storms. The month has brought a very different flavour to parts of the country, compared to September's weather. October started with summer-like warmth in Ontario and Quebec, while the West endured some chilly temperatures. That pattern has since flipped. But there haven't been many of your typical fall storms this season, making for a super-dry pattern in many areas in Canada. Let’s dive into why the storms are absent so far. DON'T MISS: What does a classic fall storm look like in your part of Canada? What fuels fall storms? A split flow, in which the jet stream literally splits in two, will prove a prominent feature during the second half of October, promoting a less-consolidated jet stream that would otherwise impact the coast of British Columbia throughout autumn. Some of that energy is being redirected down toward California, a change that’s significantly affecting our weather patterns across Canada.

An October nor'easter is developing in the Atlantic, where it will bring high surf, rip currents, coastal flooding, winds and rain to parts of the East Coast for several days this week. The National Hurricane Center has it highlighted as an area to watch this week for potential subtropical development. However, regardless of development, this system will bring dangerous conditions to the East Coast this week. Fortunately, this system doesn't look to be as strong as the one in September. But the bad news? It could linger for much of the week, so impacts could have a longer duration than you would think. There are currently coastal flood alerts across parts of coastal North Carolina and Virginia, where anywhere from 1 to 4 feet of inundation is possible. Key takeawaysWe do not expect this storm to be as strong as the late September nor'easter. The area most likely impacted the longest appears to be from the Delmarva Peninsula to eastern North Carolina, with more models pointing to primarily eastern North Carolina.