How Long Will the Smoke Last?

The worst period of hazy, unhealthy air in New York City will last from Wednesday afternoon through Thursday morning, according to a New York Times analysis of computer forecast models. The haze will most likely vary in thickness through the overnight hours and could last through the day Thursday.

The Washington, D.C., region can expect dense smoke to arrive Wednesday night and last into the day Thursday.

Forecast models for smoke near the surface show that from Thursday night into Friday, the main swath of dense smoke could move further west, into western Pennsylvania and Ohio.

Places like Toronto may get a burst of more dense smoke early Thursday as the storm system pushes the smoke further west and before it crosses the Great Lakes into the United States. In Toronto and other places, haze and smoke density may vary and change hour to hour through Friday, with possible improvements this weekend.

However, the further into the future you go, the less confident forecasters are in predicting the effects and density of the smoke.

That is partly because the high-resolution computer models get refreshed once an hour and are distributed a little less than a day in advance. Also, the models can’t predict how much smoke the wildfires will produce over the next several days.

This has been a perfect weather scenario to create extremely unhealthy air. A persistent blocking pattern has locked the weather in place, leaving a storm system hovering near Nova Scotia and pushing strong northerly winds over the Canadian wildfires.

Strong wind has kept the smoke together and nearer to the surface as it pushed into the United States. If there had been calmer winds, the smoke would have risen and dispersed more in the atmosphere, making it less concentrated.

The weather pattern may finally break down this weekend, and by Sunday the winds may shift, providing relief from the smoke. Relief could come even earlier if progress is made on putting out the wildfires.

Don’t hold your breath, though; experts say this is only the start of wildfire season in North America.