As Boston enters into the second day of what’s expected to become a heat wave, GBH meteorologist Dave Epstein told Morning Edition what we can expect in the coming days and what heat waves mean in a warming climate.

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How long will this heat last?

"I think we're going to stay at or above 90 in many areas here right through Sunday," Epstein said.

He said the heat will be oppressive in Greater Boston later today.

Thursday is forecasted to be one of the hottest and most humid days of the summer, with a high around 93.

Friday will provide a little relief with lower humidity, but still a lot of heat, around 93 again.

Temperatures will likely stay hot Saturday and Sunday, around 95 and 94. Epstein said he expects more cities and towns to declare heat emergencies.

Can we expect any breeze to help cool things off?

Tuesday's breeze may have helped make things feel a little less oppressively hot. That breeze is, unfortunately, not sticking around for the whole heat wave.

"The ventilation yesterday was definitely helpful," Epstein said. "Today we won't have as much ventilation, as much wind movement. Tomorrow we get a little bit back, so even though it's going to be very humid, that may help slightly."

The weekend will be breezier too, but with highs in the mid-90s, it can only do so much to help things feel more bearable, Epstein said.

A National Weather Service Map of Massachusetts, Rhode Island, and Connecticut showing almost the whole region under a heat advisory, with the exception of the Cape and islands and parts of central and western Massachusetts. Heat values are expected to reach 95-103 degrees.
The heat will keep blanketing most of southern New England Wednesday, July 20.
National Weather Service

What constitutes a heat wave?

A heat wave is three days in a row of temperatures at 90 or higher, Epstein said. That means that, as of Wednesday morning, it's not yet official.

"Right now, we're in day two of what's potentially going to be an official heat wave," Epstein said.

How common is this heat for Boston? How is climate change affecting the temperatures we feel?

Heat waves are not uncommon, Epstein said. But the number of 90-degree days in Boston is increasing.

"Sometimes I think, 'What did they do in 1911 when it was 104 degrees in downtown Boston?'" Epstein said. "If you look at the number of heat waves each summer, the actual number of three days in a row may or may not be going up that much. But what is going up are the number of 90-degree days, and that's definitely changed and has gone up precipitously over the past several decades."

Other parts of the country and the world are also seeing dangerous heat waves, some with high death tolls. Is this related to what we’re experiencing?

The jet stream tends not to stop at border crossings, Epstein said. Though weather and climate can look different across the world, we are all subject to some of the same forces.

"No matter where you are, this is occurring in this background of climate change," Epstein said. "Things that occur with climate change are generally more likely to occur as we get warmer."

The differences can be subtle, like a heat wave that lasts one day longer or highs that are 2 degrees warmer than they would have been 200 years ago.

"It just starts moving the needle on all of these things that have occurred before" Epstein said. "It just moves it warmer, you know, we're just turning the dial up."

How will this heat affect the drought?

Like a damp towel left out on a hot, breezy day, the soil in New England also dried out this week. That's concerning for a region already experiencing drought.

"What's interesting is that the long-term climate models say that New England is basically going to be as wet, if not wetter, than it is now in the coming decades," Epstein said.

But that rain might look different.

"We may get all of our rain in bigger spurts and we may have longer periods of dry weather," Epstein said. "As of yet, I looked at 100 years' worth of data, and we have not increased the number of droughts here in New England. We'll have to wait and see how the models bear out in the coming decades."

How do you handle the heat?

Epstein said he's an early riser anyway, but he does modify his schedule on very hot days. At 6 a.m. Wednesday, he had already gotten up, gardened, and walked his dog. During the hottest part of the day, he'll probably be indoors.

"On cooler days, I might go to the gym in the morning and then enjoy the afternoon outside," he said. "But now I'm at the gym in the mid-part of the day because it's hot, so why not go inside? Why not do those things inside when I don't want to be outside?"

How do you keep your plants happy through the heat?

Water, water, water.

"You almost can't overwater plants this time of the year unless they're sitting in a pool of water," he said. "Things are just drying out real fast."

He did recommend people try and avoid getting the leaves wet, as that can promotes disease in some plants.