Mark Herz: This is GBH’s Morning Edition. The ongoing drought and windy conditions caused brush fires this week, with smoke spreading across the region. So we turn to our GBH meteorologist Dave Epstein for our weekly science deep dive, this time on the lack of rain and the impact it’s having. Good morning, Dave.

Dave Epstein: Good morning, Mark. Good to be here.

Herz: Thank you. Thank you. Good to have you. And so how do we measure the drought? Like, how long has it been? How bad is it? Give us the expert take on that.

Epstein: Yeah. So, Mark, the droughts this time of the year are not typically going to be as bad as we would see if we were having a drought, say, in late spring and through the summer, because the amount of moisture that’s being evaporated out of the ground isn’t quite as severe and the leaves are falling off the trees. Nevertheless, we are in drought and some of the municipalities across the area have asked for water restrictions. The reason we have the drought is because we are in one of the driest — certainly top 10, top five, we’ll have to wait and see just how much precipitation we get, you know, before we close out October. But we’re going to end up with probably 2 or 3 top dryest Septembers-Octobers on record. We’ve only had 2.02 inches of rain up through. We’ll have to see what fell in the rain gauges last night. But generally, it’s been a very dry autumn across the area.

Herz: And what’s behind that?

Epstein: Well, we’ve had high pressure in control across the east. And the high pressure means that the air is sinking from above. So air is either going up or coming down. When the air is rising, it cools, condenses, forms clouds and precipitation. When we have the air sinking, it warms, it dries, it doesn’t allow clouds of precipitation. And we’ve just had, really, a plethora of high pressure in control. That’s one of the reasons why even tropical systems haven’t made it in here this fall. So we are dry.

Herz: Well, in addition to these brush fires, what are the impacts of the drought that we might continue to see if it keeps going on?

Epstein: Yeah, I mean, the drought is not going to continue to go on through the rest of the fall and the winter. At some point, we’re going to start raining again and we’ll get back to average. But we haven’t had measurable rain before last Tuesday, since the 13th and the 14th. Then we had a little bit on the 7th. So it has been very dry. I would say this: If you’ve planted newly planted trees and shrubs in your yard, give them a drink until rainfall returns [to] more typical. But in terms of established plants, because of the time of year, because it’s cooler, the sun, angle is lower, I’m not particularly concerned about this drought. If it were to keep going, say, through November, December, January, we’d start to have problems next spring. But let’s not put the cart before the horse.

Herz: Okay. So it doesn’t sound like we have a lot of makeup homework, so to speak, in terms of like the rain we’ll need. And you think it’s coming in the not-too-far-distant future, right?

Epstein: Yeah. I mean, I think generally, even if we’re dry through the winter, we’re going to see a return to more typical amounts of precipitation. And certainly we’ll need to have some significant rain or eventually snow to kind of tamp down the fire danger. But again, this is more of a temporary thing with all of these leaves coming down, drying out. That’s why the fire danger has been so high. But that’s going to change as we get through November and into December.

Herz: Okay. Sounds like good news. Sounds like your crystal ball says we don’t need to get too worried. Now, what about these temperatures, though, Dave? It’s Halloween. Unseasonably warm. Like what has been the average temperature for trick or treaters over the last few decades, and how are we comparing?

Epstein: Yeah. So typically we’d see temperatures in the 50s and lower 60s for the last day of October, for Halloween. But we have seen — we’ve seen as cold as a trace of snow, or we’ve had a trace of snow on Halloween. The coldest maximum temperature was back in 1925. It only reached 39. But as recently as 2020, it was only 42 degrees. But we have been as warm as 81 in 1946. And as recently as 2009, we were 73. So this is going to be the warmest Halloween that we’ve had probably since 2009. We do have a chance, depending on just how warm it gets this afternoon of reaching that record high of 81. We’ll wait and see how that happens.

Herz: Okay. Bonus question: Do you have a favorite Halloween candy, Dave?

Epstein: I’m not really a candy eater, so, wrong person to ask. I’d probably say something really lame, like greens from the garden or, you know, an Asian pear or something like that.

Herz: Right, Right. Well, I think it’s wonderful that your expertise in gardening and your diet go hand in hand, so I’m not surprised to hear that.

Epstein: Well, thank you.

Herz: That was GBH meteorologist Dave Epstein talking about the impact of the drought and the beautifully warm but slightly unusual temperatures we’ve been having lately. Thank you, Dave.

Epstein: You’re welcome.

Herz: This is GBH's Morning Edition.

The ongoing drought and windy conditions created more dangerous conditions for brush fires in Salem this week, with high school classes and Halloween events canceled and smoke spreading across the region.

The Salem fire is not the only one: Dozens of brush fires were reported statewide in recent days, the state Department of Fire Services told the Associated Press. And while flames were under control Tuesday, smoke made some outdoor activities nearby risky, especially for kids, older adults and sensitive populations.

Lower-than-usual amounts of rain, along with dry falling leaves, have meant the risk of brush fires is higher than usual, GBH meteorologist Dave Epstein told Morning Edition.

“Generally, it’s been a very dry autumn across the area,” Epstein said, noting that this October will likely end up being one of the driest on record.

That’s because high-pressure systems have been in control in the region, he said.

“When the air is rising, it cools, condenses, forms clouds and precipitation. When we have the air sinking, it warms, it dries, it doesn’t allow clouds of precipitation,” Epstein said. “And we’ve just had, really, a plethora of high pressure in control. That’s one of the reasons why even tropical systems haven’t made it in here this fall. So we are dry.”

Officials with the Department of Fire Services asked Massachusetts residents to remember that bonfires and other forms of open burning are banned statewide through January. Residents should dispose of cigarettes and fireplace ashes responsibly, ideally dousing them with water and keeping them in metal.

Epstein said fall droughts tend to have less of an impact than spring and summer ones.

“The amount of moisture that’s being evaporated out of the ground isn’t quite as severe and the leaves are falling off the trees,” Epstein said. “Nevertheless, we are in drought. And some of the municipalities across the area have asked for water restrictions.”

But we can expect the rain to return at some point soon.

“The drought is not going to continue to go on through the rest of the fall and the winter. At some point, we’re going to start raining again and we’ll get back to average,” he said. “Even if we’re dry through the winter, we’re going to see a return to more typical amounts of precipitation. And certainly we’ll need to have some significant rain or eventually snow to kind of tamp down the fire danger. But again, this is more of a temporary thing with all of these leaves coming down, drying out. That’s why the fire danger has been so high.”

Epstein suggested giving newly planted trees and bushes a bit of extra water, but said more established plants will likely be able to weather the drought.

“If it were to keep going, say, through November, December, January, we’d start to have problems next spring,” he said. “But let’s not put the cart before the horse.”

Halloween will likely be partly sunny and warm, with highs possibly reaching the low 80s, Epstein said.

That’s warmer than average — possibly the warmest Halloween since 2009, when the high was 73. But it’s not completely unheard of: Boston recorded a high of 81 in 1946.

“Typically we’d see temperatures in the 50s and lower 60s for the last day of October, for Halloween,” Epstein said. “We’ll wait and see how that happens.”