Why is the sky so hazy? Smoke from wildfires in the west

Wild fires out west made for a hazy evening fishing in Squantum with the Boston skyline in the backround.Stan Grossfeld/Globe Staff

Smoky skies are settling in over New England this week because of distant wildfires burning across Canada and the western part of the United States.

One of those — the Bootleg Fire — has been burning for two weeks in southwestern Oregon and has consumed more than 364,000 acres, according to Oregon fire officials. It’s the largest wildfire in the United States so far this year.

While it’s hard to predict how long the haze will hang around New England, National Weather Service meteorologist Alan Dunham said Tuesday that it could be a while.

“It’s going to depend on how the jet stream sets up over the next few days,” Dunham said.

Boston’s air quality will be affected as the wildfire haze drifts over the region.

Tuesday’s air quality was in the moderate zone, according to a forecast by the Mass. Department of Environmental Protection. On Wednesday, the air quality will improve slightly and by Thursday, Boston’s air quality is expected to be back in the healthy zone.

Officials recommend that people who are unusually sensitive should consider reducing exercise outdoors as some pollutants may be a moderate health concern for a small group.

Rhode Island received an air quality alert Tuesday due to heavy smoke from the Canadian wildfires.

According to an announcement from the Rhode Island Department of Environmental Management, heavy smoke from the wildfires is causing elevated fine particle concentrates that are affecting the entire state, reaching “unhealthy levels.”

Climate change is wreaking havoc across the western US, where a dangerous heatwave has killed hundreds of people in recent weeks.

As the climate warms, the west is increasingly primed for disastrous wildfires. More than half of the acres burned in the western US each year can be attributed to climate change, according to a 2016 study. Without aggressive action to reduce greenhouse gas emissions, another study found that forests in Northern California, Oregon, and Washington could see an increase of more than 78 percent in area burned by 2050.

Sabrina Shankman and Alexa Gagosz of the Globe staff contributed to this report.