Hot Saturday: Looking back at New England's hottest day ever

A rather extreme heat wave gripped New England for several days this June. This heat wave was the longest recorded heat wave in Hartford. Feels-like temperatures skyrocketed to around 110° in places as the air temperature reached into the upper 90s with dew points well into the 70s. Still, this heat wave came up short of all-time records in New England. Many of these records still belong to August 2nd, 1975, New England's hottest day on record in many places.

The heat for this fateful Saturday, now known simply as "Hot Saturday," began to build across the center of the country earlier in the week. This came as a strong ridge of high pressure, now known as a heat dome, began to build. On Wednesday, July 30th, 1975, temperatures soared well into the 90s and low 100s across the upper Midwest while New England hung around the 80s.

This strong heat dome continued to shift east through the week. By Friday, the system was situated near the New York, Pennsylvania border. This position is very favorable to pump heat and humidity into New England amid a southwest flow around the area of high pressure. This allowed heat to build into the 90s for much of New England. More importantly, high humidity kept overnight lows very warm. Boston's morning low on August 2nd was an incredible 83°.

Weather setup on August 2nd, 1975:

Photo byNOAA

On August 2nd, the high remained in place, and with a very warm start, temperatures across the region soared to truly extreme levels. The temperatures reached on this day are just about as high as what's possible in New England. Numerous records were set across New England.

First and foremost, this day saw the hottest temperature ever recorded in New England. This was 107°, recorded in both Chester and New Bedford, Massachusetts. Rhode Island would record their state-wide record when it reached 104° in Providence.

Triple digit temperatures were extremely hard to escape; not even the coast brought a reprieve. Portland, Maine and Portsmouth, New Hampshire saw all-time highs at 103° and 102° respectively. Even the typical cool spot of Nantucket recorded a 100° reading. This is the only triple digit high temperature in Nantucket's recorded history.

Photo byBoston City Archives

Some relief could be found at the region's highest points. Mt. Washington's summit saw a high of 72°. While this is much cooler comparatively speaking, this is actually the all-time record high temperature at the summit. For comparison, the average daily high temperature in August is 54°. The summit did reach 72° one other time in June of 2003.

Thankfully, this extreme heat did not stick around for very long after Hot Saturday. August 3rd would only see temperatures rise to 89° in Boston as the heat dome sank south of New England. The heat dome's southward progress continued on August 4th as an area of low pressure moved toward the region. Boston's high just two days after Hot Saturday only managed to reach 72°.

Weather map from August 2nd, 1975. Note the forecaster's hand-written note at the top of the page:

Photo byNOAA

The only other day in New England's history that could potentially be compared with August 2nd, 1975 is July 4th, 1911. On that day, Boston experienced their all-time high temperature that still stands today: 104°. Three New England states saw their all-time record highs set on the Fourth of July 1911: Maine and Vermont reached 105° and New Hampshire reached 106°.

The first half of July 1911 was likely New England's most extreme heat wave ever recorded with extreme heat persisting for an astonishingly long time for the region. In fact, Maine's 105° record on July 4th would be matched on July 10th of that year. While the 1911 heat wave was extreme with all-time highs still standing over 100 years later, August 2nd, 1975 stands as the single hottest day in the region's history, highlighted by the 107° all-time high that was just missed in 1911.

Sources: Weather.gov; Boston.com; NOAA; Mt. Washington Observatory