New York and parts of the eastern United States and Canada were shrouded in a gray smoky haze yesterday from fires burning in the western US and Canada.

New York state's environmental protection services issued an air quality advisory, automatically triggered when fine particle matter is expected to rise above 35 micrograms per cubic meter of air.

An expert from the agency said it is not uncommon for smoke from fires in the west of the country to reach the New York area, but they usually remain high enough to not affect air quality. This time, the smoke was lower than usual, the expert said.

The phenomenon was set to dissipate today with the arrival of a cold front in the New York region, said a spokesperson for the US National Weather Service.

Several large fires have ravaged the western United States in recent days - notably in California, Nevada and Oregon, where the dangerous Bootleg Fire is still raging, even though the fire season has only just begun.

In Canada, more than 2,000 people have been evacuated in recent days in the province of Ontario, the most populous in the country, and more than 200 fires were active in the province and neighboring Manitoba, according to official figures today.

Canada's western province of British Columbia also declared a state of emergency yesterday, with wildfires expected to grow even larger in the coming days due to high heat and winds.

"We have reached a critical point," said provincial public safety minister Mike Farnworth.

"Based on the advice of emergency management and wildfire officials, and my briefing last night on the worsening weather, I am declaring a provincial state of emergency."

The decision empowers officials to organise mass-scale evacuations and to provide emergency accommodation for evacuees, he added.

Some 5,700 people were under evacuation orders in the province yesterday - more than double the previous day's tally, as the threatened region grew in size.

Around 32,000 more residents have been placed on alert.

"Please have an evacuation plan ready for your family," said Cliff Chapman, the director of operations for British Columbia's wildfire service.

"From working in this branch for 20 years, I would be taking my family out if I was on an evacuation order today."