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 likely be celebrating outside amid hot and humid temperatures.

Back when our Founding Fathers fought for freedom, independence wasn't the only battle John Adams faced in 1776.

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. 

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.

"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.

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.

In 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.

A 250-year-old history reminds us that, despite the challenges we face, it only takes one step to declare change.