Summer haze in November? Air pollution spiked along with the temperature in Hamilton Monday

Hamilton's record-breaking November heat also came with an unwanted summer haze in the lower city Monday.

A visible smear of air pollution - mostly fine particulate and nitrogen dioxide - briefly spiked into high-risk" levels on the provincial air quality health index for downtown Hamilton around 1 p.m.

That appears to be the worst recorded air quality on the downtown index all year.

Puzzled residents looking down from the Mountain Brow noted the visible haze over Lake Ontario and the nearshore lower city, prompting a discussion online.

Despite record-breaking November temperatures in the twenties, Ron Jones decided to stay inside Monday when he saw levels of lung-busting dust pollution jump into the danger zone on an air quality monitor at his bayfront home.

It was bad ... you could smell it," he said Monday evening. On days like these, I run the furnace fan and keep the windows closed."

His results mirrored those of home monitors across the central and east lower city that are part of a University of Toronto local air monitoring experiment. That map showed orange and red dots at volunteer homes that represented fine particulate pollution levels between 100 and 162 micrograms per cubic metre of air. (Clean air dots are green.)

Red levels pose a health risk to a person with asthma or other breathing conditions with prolonged exposure. At the high end of the range, other residents could also experience health impacts.

The good news is the pollution spike was relatively brief, according to Gary Wheeler, a spokesperson for the provincial Ministry of Environment, Conservation and Parks.

The elevated pollution levels were driven by a short-lived" temperature inversion, which occurs when a layer of warm air develops on top of a layer of cool air and temporarily traps contaminants close to the ground. That can be a particularly noticeable phenomena in a lower city that still boasts plenty of active industrial smokestacks.

Normally, air quality lingering in the high-risk" category would prompt a special air quality statement, but the spike was both unexpected and too brief to warrant a warning, Wheeler said.

(Worth noting: Hamilton has not had a smog warning" since 2013.)

Temperature inversions occasionally occur during unsettled weather in fall. Their pollutant-trapping potential is sometimes more noticeable for those living in the lower city than for residents 90 metres higher atop the Mountain.

But in this case, a haze was also visible Monday in other lakeshore cities like Toronto, said Environment Canada meteorologist Peter Kimbell.

Kimbell said it appears pollutants had recently been pushed out over the lake and accumulated" rather than dissipating - leaving nearshore residents to breathe in the hazy results during the last few warm, still days.

The good news is the air was clean again both below and above the escarpment Tuesday morning.

The bad news is the highly unusual" summer fling with T-shirts in November is almost over, Kimbell said. The city is poised to smash a 1970s November heat record Tuesday if Hamilton reaches a forecasted 24 degrees.

But temperatures will begin dipping backing toward the seasonal average later in the week.

Matthew Van Dongen is a Hamilton-based reporter covering transportation for The Spectator. Reach him via email: mvandongen@thespec.com