Humid + hot = miserable

By Laura J. Nelson, Matt Rocheleau, and Jaime Lutz, Globe Correspondents

As an intense heat wave gripped the region, the National Weather Service this afternoon issued an “excessive heat warning’’ that will remain in effect until 6 p.m. tomorrow.

The warning was announced as temperatures are expected to hit 100 degrees in parts of Eastern Massachusetts tomorrow, after two days where temperatures were in the 90s. Combined with high humidity, the heat index values could hit 107 degrees tomorrow.

As Boston sweltered today, city employees armed with bottled water and paper fans knocked on hundreds of doors in the North End, checking to ensure that older residents were staying cool.

“Is there anything you need?” said Emily K. Shea, commissioner for Affairs of the Elderly, as she peered into the Astonia Housing Complex apartment of Margaret Flynn, 85.

“I’m just glad I got my air conditioner replaced,” Flynn said, smiling. “It gets pretty hot up here.”

City employees checked on more than 28,000 seniors through door knocks or automated phone calls today, officials said.

Alan Dunham, a meteorologist at the National Weather Service in Taunton, said temperatures in the 90s with high humidity made it feel like it was a steamy 104 degrees.

Boston is approaching, but will not quite reach record temperature for today, which is 102 degrees in 1977, said Dunham.

At 3 p.m. today, the official Boston temperature was 97 degrees.

There is no end in sight, as the heat wave is not expected to break until Sunday.

“It’s mainly just going to feel miserable,” Dunham said.

A heat advisory is in effect in Boston from noon to 9 p.m today. By week’s end, the region is expected to have suffered through the first official heat wave, which is defined as three or more days with 90 degrees or higher.

In Brighton, mail carrier Don Laffey had little choice but to endure the swelter.

“The good days are few and far between … during the spring and the fall,’’ Laffey, who has been delivering mail for the past 26 years, said as he exited one apartment building lobby and headed for the next. “But, I don’t mind it.”

The worst part of his morning and early afternoon route is when he changes to the opposite side of Commonwealth Avenue, where there’s less shade.

“When you go to the other side of the street, it’s like you’re in a different atmosphere. It’s 20 degrees hotter,’’ he said. He pointed toward a row of apartment- building lobbies across the street where he will later stand and spend several minutes sorting mail into each unit’s bin.

“It’s like an incubator in there,’’ he said.

Laffey said his 20-year-old son, Scott, a Marine, is scheduled to return home from Afghanistan in 19 days.

“I put everything in perspective,’’ the mail carrier said. “My son’s in out in Afghanistan right now. It’s 120 degrees everyday over there.”

Concerned that the intense heat and humidity will put people at risk, Boston and other municipalities have opened cooling centers; some communities, like Boston, are keeping municipal pools open for extended hours.

Officials are also urging residents to check on senior citizens in their neighborhoods, to minimize strenuous activity during the hottest periods of the day, usually mid-afternoon, and to keep hydrated.

Dunham, the meteorologist, said winds will be gusty today, but even those strong winds won’t bring cooling relief. Because the winds hail from the southwest, “they’re going across mainly land, so all it’s going to do is blow over hot land to give you hot air,” Dunham said.

With plenty of humidity, and lows in Boston in the upper 70s, conditions will be uncomfortable for those without air conditioning, “it’s going to be a lousy night for sleeping,” Dunham said.

He added, “You might want to rent a hotel room. Or just stay at work. It will show dedication!”

For the rest of the state, hot conditions won’t give way tomorrow. An excessive heat watch is in effect for Friday afternoon when temperatures could reach 100 degrees.

Combined with humidity, tomorrow afternoon could feel like 105 degrees – or even greater, Dunham said.

Saturday will continue to have temperatures in the 90s, but humidity will be lower, making the day slightly more comfortable, Dunham said.

But the first real break from the heat wave won’t come until Sunday when highs are only in the lower 80s. “Compared to what we have today and tomorrow, highs in the lower 80s will feel wonderful,” Dunham said.