New Jersey Gov. Phil Murphy called the Canadian wildfire smog blanketing the Northeast an “unprecedented” event as he urged locals to stay home and avoid the outdoors.

“The widespread nature and uncommonly high levels of fine particulate concentrations reaching the unhealthy category is of a historic magnitude,” he said in a press conference this morning.

An air quality action day alert issued for todday was upgraded to the “unhealthy” category and the alert was extended to the end of tomorrow. 

Murphy said the air quality index reached 226 in Jersey City at 7 a.m. and in South Jersey, it hit 285 — both within the unhealthy range. 

An AQI at or below 100 is considered satisfactory, according to the Environmental Protection Agency's website AirNow.gov, but when it is above 100, air quality is considered unhealthy. 

“Poor air quality impacts everyone,” Murphy said, noting exposure to high levels of particulate matter “can cause difficulty breathing, chest pains, and asthma attacks.”

The National Oceanic and Atmospheric Administration confirmed today that El Niño — a naturally occurring climate cycle that influences global temperatures, rainfall patterns and severe storm systems — is back.

What does that mean for wildfires? Canada is already experiencing an intense start to its wildfire season, and El Niño conditions could make matters worse. The weather pattern is typically associated with more volatile tropical storms and hotter, drier conditions across the northern parts of the United States and Canada.

Canadian officials have said that hot and dry conditions will likely persist into the summer months, increasing the risk of wildfires through August.

Also of concern are the health risks when regions experience poor air quality at the same time as heat waves. Together, extreme heat and high levels of air pollution can put an extra strain on the body and can increase the risk of respiratory, cardiovascular and kidney diseases — particularly in vulnerable populations such as children, the elderly and people with pre-existing health conditions.

Senate Majority Leader Chuck Schumer, D-N.Y., has sent a letter to Agriculture Secretary Tom Vilsack asking him to direct resources to fighting the wildfires in Canada that have produced the heavy smoke affecting air quality on the East Coast of the United States.

“The best way to ensure the U.S. does not suffer another wave of wildfire air pollution is to contain these fires up in Canada as soon as possible,” he said on the Senate floor this morning, “That’s getting at the source, and that’s what we need to do.”

Schumer also said the letter calls on Vilsack to “double the number of personnel to mitigate the risk in the air for millions of Americans.”

“To walk through New York City yesterday was to walk on another planet,” he said, “The orange fog of wildfire smoke left our city unrecognizable.”

The Smithsonian’s National Zoo in the nation’s capital will be closed today “due to the poor air quality,” the iconic facility said in a tweet. 

The closure is for “the safety of our animals, our staff and our guests.” 

It comes as a "code purple" air quality alert was issued for Washington, D.C., today, meaning the air quality is very unhealthy. Under such a warning, all people should stay indoors as much as possible and wear N95 or KN95 masks if outdoors. 

The Federal Aviation Administration said Thursday morning that it had delayed all flights bound for New Jersey’s Newark Liberty International Airport nationwide. It also grounded departures to Philadelphia International Airport due to low visibility.

Some pet owners are finding creative ways to safely take their dogs for walks, like buying or making masks for their pets, as smoke from the Canadian wildfires continues to wreak havoc in states across the U.S.

Not all the dogs are into it though.

The Environmental Protection Agency's "AIRNow" app has reached No. 12 on Apple's app store ranking for all free apps, and sits at No. 1 in weather apps.

The app provides people with a quick way to check current air quality and air quality forecasts.