Jeremy Siegel: This is GBH’s morning edition. Window-shattering heat. That is how warm it is this week.

Paris Alston: Yes, the city of Boston is once again under a heat emergency. And just yesterday, city inspectors said a window pane on the 13th floor above TD Garden shattered due to the high temperatures, raining glass on the sidewalk below. For more on this and the forecast, we are joined by GBH meteorologist Dave Epstein. Good morning Dave.

Dave Epstein: Good morning. Good morning.

Alston: And I understand you have to welcome back Jeremy. You haven’t seen him in a while.

Epstein: I was just going to. I was just going to say, I had to say Mazel tov. I’m so happy for you. And, welcome home, welcome back.

Siegel: Thank you. It is great to be back after parental leave, and I’m very excited to have someone who I can count on to give me answers to questions about the weather and interesting science things. Before we do get into the forecast itself, do you have any idea how heat causes a window to break?

Epstein: You know, I’m making things up here. I mean, part of it may be if the air conditioning was really cold on one side and the heat on the other, and you’ve got that big temperature contrast that could have perhaps done it. You know, it’s like if you pull out a bowl that’s really cold and you put it in the oven too quickly, it can crack. So off the top of my head, that might be what it was. But, yeah, I mean, we have a little cottage, and the sun was reflecting — this happened, two years ago in the heat wave. The sun was reflecting off the skylight, and it melted the siding. It was just, you know, it’s like that vinyl siding, and it literally melted it. So, you know, there was no record high temperatures yesterday. So it’s probably something more weird about the glass rather than the temperature itself.

Alston: Well, I just hope no one was walking on the sidewalk where, the glass shattered there and didn’t get hurt. And we haven’t seen any reports that anyone has, so that’s good. So Dave, no record temperatures yesterday, but it is going to be hotter today than it was. Tell us more.

Epstein: Yes. The temperatures yesterday reached 95 in the city of Boston. I think today will be a very similar kind of a day as well tomorrow, you know, whether it’s a degree above or below, it’s not going to really make any difference in the way you feel or the weather itself. So we do have definitely a hot day for today. The dew points are up there. Heat indices are going to be in the mid- to upper-90s to low 100s. And that means that the weather service has issued a heat advisory. We don’t have a high heat warning that would get issued if the heat indices were going to be 105. We also, have something else called the wet bulb temperature, which maybe we can explain in one of our Thursday deeper dives into that. But that wet bulb temperature will also be approaching numbers near 90 degrees, which means that it is very uncomfortable to work outside and also gets a little dangerous if you’re outside doing heavy work in the middle of the day.

Siegel: So it’s hot, dangerous and uncomfortable outside during the day. But let’s talk a little bit about nighttime temperatures overnight. Breeze is usually what kind of saves us in the summer when you can toss open the windows, cool off when it’s dark out. That has not been the case lately. What’s up with that?

Epstein: Yeah. You know, it’s a great question. And the minimum temperatures at night have actually been increasing faster than the daytime temperatures. So you know, as the climate warms, we’re warming. But it’s not even. The nights are actually warming faster than the days. This is the case in the winter as well. And one of the reasons for that is that the temperature can only go down to the dew point. The dew point is the amount of moisture in the air. In a warmer climate, you have more moisture. So if you have more moisture, that bottom rung of low temperatures is not as low anymore. So for example, Boston has not gone below 70 — I’m just looking — since the 8th of the month. And we were at 67 on that day. So today is the eighth day in a row not going below 70 degrees. And that’s quite a stretch.

Alston: Yeah. Pretty substantial. And Dave, we have talked about, you’ve told us about how with the changing climate, we see more of these hot weather days over time. So is what we’re seeing right now considered normal for how we’re tracking in that regard?

Epstein: Yeah, I mean, it is within the realm of normalcy. And actually, Boston has only reached 90 twice this month. So it’s not like, you know, we’re looking out going, wow, this is just unprecedented. It’s not unprecedented. I think the things that are really at the top of the game here are the amount of humidity, that’s definitely way up there, if not at number one, but pretty close in terms of the high dew points. So the humidity is really the thing that is unusual, more so than the temperatures. We’re running right now in Boston, 3.5 degrees above average for the month. We’ve only had two days at Logan Airport — don’t get me started about why it’s there, but if you went out to Jamaica Plain, were more at eight or nine days at 90 degrees. So, but, you know, officially at Logan, only two.

Siegel: That is GBH meteorologist dave Epstein. On Thursday, Dave will be joining us for his weekly deep dive into the science behind warming ocean waters this week. Dave, thanks so much. Look forward to talking to you later this week.

Epstein: We’ll talk to you then.

Alston: You’re listening to GBH news.

Meteorologist Dave Epstein is our go-to person for pressing weather questions on everything from winter blizzards to summer droughts. He’s also a horticulturist, meaning he’s an expert in anything that grows leaves and flowers. GBH’s Morning Edition asked our audience for weather and gardening questions, and Epstein graciously answered them on the air.

Have a gardening or weather question for meteorologist Dave Epstein? Email us at   thewakeup@wgbh.org or text 617-300-2008.

Why is it so hot at night?

Daytime temperatures reached 95 in Boston Monday and will climb toward 98 on Tuesday.

“It is very uncomfortable to work outside and also gets a little dangerous if you’re outside doing heavy work in the middle of the day,” Epstein said.

And sunset offers little respite: Boston hasn’t seen a nighttime low under 70 since July 8, GBH meteorologist Dave Epstein said.

“And that’s quite a stretch,” he said.

As the climate warms, we are seeing nighttime temperatures climb faster than they do in the daytime, he said.

“We’re warming, but it’s not even,” Epstein said. “The nights are actually warming faster than the days. This is the case in the winter as well. And one of the reasons for that is that the temperature can only go down to the dew point.”

The dew point is a temperature meteorologists use to determine how much moisture is in the air. The higher the dew point, the more humid the air can be.

“In a warmer climate, you have more moisture,” Epstein said. “If you have more moisture, that bottom rung of low temperatures is not as low anymore.”

So far this July, Boston is 3.5 degrees warmer than average, Epstein said. Boston’s official temperature is taken at Logan Airport, which tends to be a bit cooler than other parts of the city because it’s so close to the water.

“If you went out to Jamaica Plain, were more at eight or nine days at 90 degrees,” he said. “But officially at Logan, only two.”

The heat can make things dangerous, especially for people working, exercising or spending a lot of time outdoors, Epstein said.

Stay safe by taking breaks, drinking a lot of water and not over-exerting yourself.