A firefighter cools off while fighting a five alarm fire in the Dorchester neighborhood of Boston, July 21, 2019. (Christi Christo/The Boston Herald via AP)

A number of major New England cities will see July go down in the books as their warmest month on record, thanks to a combination of a steamy weather pattern and the effects of a changing climate.

Boston, where airport weather records date back to 1936, saw July clock in at more than five degrees above average for the month. Through the thirtieth, the average temperature — which takes into account both daily highs and lows — stood at 78.5 degrees. The city of 700,000 hit 98 degrees on the 21st. Six of the top 10 warmest months on record in Boston have taken place in the past ten years.

“This is clearly a problematic summer trend for Boston,” wrote Eric Fisher, the chief meteorologist at WBZ-TV in Boston. “It’s a combination of the warming climate, much warmer than average ocean temperatures, and the urban heat island effect.”

It was a similar story at Bradley International Airport, which serves the greater Hartford region. Their average July temperature stood at 78.2 degrees as of July 30, which was 4.6 degrees above average. Seven of the top 10 warmest months on record at Bradley have occurred in the past 20 years, with records at the airport being kept since 1949.

Farther north, Portland saw their warmest month on record, too. Eight of Portland’s 10 hottest months on record have occurred since 2000.

Nearby in New Hampshire, Manchester-Boston Regional Airport saw their warmest month on record as well.

Think it’s a bit too early to be calling these records when the month hasn’t even ended yet? Think again. Even if Manchester dropped below 40 degrees tonight, they would still beat out their second-place contender. Nine out of the top 10 warmest months on record in Manchester, where bookkeeping began in 1948, have occurred since 2006.

Are you noticing a trend here?

It’s no coincidence that many of the Northeast’s warmest months have occurred in recent memory, given the effects of climate change. This especially obvious in Boston, where only one day saw a record warm daily maximum temperature during July. Yet somehow Boston still managed to claim their record warmest month. How?

“Our monthly records come from persistence and not shorter stints of extreme heat,” Fisher explained in a tweet. However, Fisher says the highs “weren’t slouches either,” citing a year’s worth of 90-degree days all landing within a month.

One symptom of the evolving climate is that nights are becoming disproportionately warmer. Increased humidity, combined with the urban heat island effect that keeps urban areas warmer than surrounding suburbs at night, can trap heat near the surface, raising nighttime temperatures. The growing concentrations of greenhouse gases in the atmosphere also are more efficient at increasing surface temperatures at night, when the atmosphere is more stable, than during the day.

Another key contributor to New England’s warmth, which itself is partially tied to climate change, is higher than average sea surface temperatures off the East Coast. This helps usher in milder and more humid air masses, boosting average temperatures further.

Andrew Freedman contributed to this article.