The heat is on -- big time.

A searing, blazing spell of near-record daytime highs and tropical humidity, with especially steamy overnights, has engulfed the Berkshires and most of the eastern U.S. in what's turning out to be the hottest summer locally in 11 years.

To make matters worse, there's no relief in sight until late Friday or Saturday, said National Weather Service meteorologist Ingrid Amberger in Albany, N.Y.

"It's been a sticky summer so far," said Amberger, an NWS lead forecaster, with deliberate understatement.

She expects portions of the Berkshires to sizzle into the low 90s every day this week, with Wednesday shaping up as the hottest. Humidity levels will remain high, adding to the overall discomfort.

But, unlike neighboring areas such as Litchfield County, Conn., and New York's mid-Hudson Valley, Amberger is not expecting the heat index to exceed 100 in the Berkshires. The index is a combination of temperatures and humidity according to a formula similar to wind-chill readings, she said. For 100 or higher, heat advisories are issued urging the public to take common-sense precautions.

"The problem is that at night, when temperatures don't cool off as much as usual, we don't get any relief," said Amberger.

Monday's mid-afternoon high of 87 at the Pittsfield Airport was one degree shy of the record, 88, set in 1979.

Under the dome of a westward-expanding hot-air pump known as the Bermuda High, the prolonged heat spell has been persistent, with few breaks. Since June 21, temperatures have been substantially above normal every day, as recorded at Pittsfield Municipal Airport. Normal high at this time of year is 79, with an overnight low of 56.

By Saturday, after a round of potentially severe thunderstorms, relief will be noticeable with temperatures returning to seasonable highs in the upper 70s to low 80s for the rest of the weekend into early next week.

Although electricity demands are massive with air conditioners running at full blast, ISO New England, which is the power-grid operator for the six-state region, reported power consumption topped out at just over 26,100 megawatts at 4:30 p.m. on Monday. The power grid issued a low-level alert to monitor power-usage demands but did not request conservation measures.

Monday's peak was below the system's all-time record high of 28,130 megawatts set on Aug. 2, 2006, during a brief but intense heat wave. The system's capacity is 32,000 megawatts . National Grid and Northeast Utilities are part of the ISO group.

Officially, a heat wave requires three days in a row of 90 degrees, as defined by the government forecasters. Otherwise, the weather professionals call it a hot spell.

"Plain and simple, this week may feel the worst of any week for this summer," according to senior meteorologist Alex Sosnowski at Accuweather.com. He described the Northeast region as a "virtual sauna bath" for the rest of the week.

"High daytime and nighttime temperatures, high humidity, intense sunshine and lack of wind will make the area seem like the middle of the tropics," he added.

Last summer in Pittsfield, there were two above-90 days in June and one in July, but no prolonged hot spells. Further back in the record books, the summer of 2002 saw two official heat waves in Berkshire County -- a three-day spell in July and a four-day ordeal in August.

The hottest day ever recorded at the Pittsfield Municipal Airport was 95, on July 3, 1966.

But the longest extended period of highs close to or above 90 came in 1988, a two-week roast during the first half of August.

Hot town, summer in the city

Here are the predicted highs and the records for each date at Pittsfield Municipal Airport:

Monday, July 15: 87, actual (88 in 1979)

July 16: 91 (89 in 1983)

July 17: 92 (91, 2012)

July 18: 90 (92, 1953)

July 19: 88 (92, 1964)

Sources: Eagle files; National Weather Service; Accuweather.com

To contact Clarence Fanto:
cfanto@yahoo.com or (413) 637-2551.
On Twitter: @BE_cfanto