While fighting for independence, John Adams dreaded Philadelphia summers. So how hot was it in 1776?

As Philadelphia prepares for our nation's 250th birthday, we'll be celebrating amid some of the hottest temperatures the city has seen in decades, possibly in history.

Temperatures are expected to reach into the triple digits this week, including on Saturday, July Fourth, when the city is throwing a party with a concert and fireworks on the Benjamin Franklin Parkway.

Back in 1776, when the Founding Fathers were fighting for freedom in Philadelphia, John Adams was also battling the heat. 

In a letter Adams wrote to his wife, Abigail, on May 27, 1776, he complained about the Philadelphia heat.

"Yet I dread the melting heats of a Philadelphia summer," Adams wrote in one of the five letters where he complained about the weather. 

"We are still parching under the fierce heat of dog days," Adams also wrote. 

In a 1777 letter, he had more to say about the unpleasant weather: "The Air of the City has been like the fierce Breath of an hot oven. Every Body has been running to the Pumps all day long. There has been no finding a Place of Comfort—the shade, and the very Entrys of Houses where they have the best Draughts of Air, have been scarcely tolerable."

Emily Sneff, of the Museum of the American Revolution, said Adams' letters reveal the challenges he and his fellow Founding Fathers faced crafting the Declaration of Independence, including the stuffiness inside Independence Hall.

The historic building has air conditioning today, but it was likely stifling when Adams was spending time there.

"They needed to keep the doors and windows closed because they didn't really want eavesdroppers," Sneef said.

So in 1776, how hot were the temperatures in Philadelphia? 

NEXT Weather meteorologist Grant Gilmore researched the notes of Adams' fellow founding father, Thomas Jefferson, who took meticulous temperature readings. 

"2026, our averages are about five to seven degrees warmer than when they were back in 1776," Gilmore said.

Jefferson's records show it was 76 degrees around 1 p.m. on July 4, 1776, and temps did get into the low 80s that month.

As cobblestones gave way to concrete, our climate's also changed.

"I think he would be incredibly surprised just by the heat radiating under his feet," Jen Brady, of the science nonprofit Climate Central, said.  

Brady said temperatures began spiking during a different revolution.

During the Industrial Revolution, emissions from factories and eventually cars began polluting our air, trapping atmospheric gases and warming our planet, pushing temperatures to dangerous levels.

"He thought it was hot, and he probably had a hot day, but it would be nothing compared to what we're experiencing now," Brady said.

While Adams, a Massachusetts native, may not have been used to Philly's humidity, he and his fellow Founding Fathers still made history.

Adams inspired generations of people to make their own declarations — that all men, all women, of all races and —  on Philadelphia's first-ever Earth Week — all species are created equal.

"Advocating for a better future; hopefully, you too, can feel as if you're part of that story," Sneef said.

And our 250-year history reminds us that, despite the challenges we face — including scorching temperatures on the nation's birthday — it only takes one step to declare change.