Dozens of brush fires continue to born across the North Shore of Massachusetts and the rest of the state. Fire crews are returning to active areas Tuesday to try to put those flames out.

The fire chief said as of yesterday, more than 250 acres had burned here in Middleton in a wildfire that has spread to North Reading.

You could see the smoke over Middleton Pond on Tuesday morning, as multiple spots in the woods are still actively burning.

But right now, these flames are not endangering any homes in the area.

Hundreds of acres burning in Massachusetts

Firefighters were driving around monitoring the fires on Tuesday morning. They’ll be back out actively putting out hot spots once the sun comes up and visibility improves.

On Monday, helicopters were hovering over the pond and grabbing buckets of water to dump on the flames.

A similar operation will happen in Canton on Tuesday morning, where another brush fire burns.

And firefighters in Salem, Lynn and Peabody will continue to battle a more than 130-acre wildfire in that has spread across those communities.

Douglas LeColst, the fire chief in Middleton, said these fires are too big to extinguish at this point without some help from Mother Nature.

“We feel confident that the majority of it is contained, (but) it’s going to burn for days," he said. "You know, we’re not going to extinguish the fire. Our goal is just to contain it, which we feel pretty confident we’re heading in that right direction. So there’s going to be smoke in the area for a considerable amount of time until we get some good rainfall. That’s what we need.”

Brush fires were also reported in other New England states in recent days. The dry conditions contributed to dozens of fires in Maine over the weekend, including one large one in Buckfield that spanned five acres. And in Rhode Island, firefighters responded to a brush and boat fire in Johnston on Monday morning.

Why do I smell smoke in Greater Boston?

Obviously the smoke from these fires is affecting a lot of us.

All over the Boston area, you really can smell the smoke from those fires due to a weather phenomenon called inversion. That's when warm air traps cool air and smoke close to the ground, and that can be a concern for air quality because wildfire smoke has been shown to carry pollutants.

"Why you might want to be even more cautious on days where there's smoke present is because of that additional toxicity," said Jennifer Stowell, from the Boston University School of Public Health. "The biggest concern is for people who already have underlying conditions."

She said that may mean limiting outdoor activities if you have a respiratory condition like asthma, and at the very least staying tuned in to air quality conditions.

Because of the wind direction in Middleton and North Reading, the air quality index in the area is between 52 and 56, according to the AirNow Fire and Smoke Map, putting it as moderate, meaning people who are sensitive to smoke should limit exposure.

But the fire burning in Salem, Lynn and Peabody is a different story. There, the air quality is considered unhealthy, ranging between 130 and 189. That means everyone should take precautions by reducing outdoor activity.

And in Saugus, which is downwind from both fires, the air quality is considered very unhealthy, at 220, where it's recommended everyone should limit or avoid outdoor physical activity.

“Air pollution in general can have both immediate and long-term effects, depends on the quantity of exposure and intensity," said Dr. Wynne Armand, as Mass General Brigham internist. "Also, some of the immediate effects on the milder side could be irritation of the throat or eyes, or even exacerbation of skin conditions like eczema, more of the serious symptoms can be difficulty breathing, coughing, chest pain, palpitations.”

Health experts say those with underlying health conditions, the very young and the very old should take extra precautions.