This weekend marks the 250th anniversary of the monumental founding moment of our nation: The July 4, 1776, Declaration of Independence. And interestingly enough, even though it’s been two and a half centuries, we know exactly what the conditions were like in Philadelphia (where all the ruckus was happening) that day.

We know it was a crisp 68 degrees at 6 a.m., and we know that it rose up to 76 (symbolic much?) that early afternoon.

What makes this weather data especially poignant is that it doesn’t come from an official record, but from one of the Founding Fathers themselves. It was recorded by Thomas Jefferson, who had just splurged on a new thermometer.

This wasn’t an isolated hobby. The people who hammered together our constitution were deeply invested in the natural world.

Jefferson kept a daily weather log for half a century. George Washington tracked storms with military precision, whether he was managing Mount Vernon or commanding troops in the field. And Benjamin Franklin didn't stop at flying a kite in a thunderstorm: He mapped the Gulf Stream, tracked hurricanes and once literally chased a whirlwind on horseback, just to see how it worked.

None of this was a coincidence. As products of the Enlightenment, the founders believed that understanding nature by closely observing it was the key to making better decisions.

The same minds drafting a constitution and executing a revolution weren’t doing so in a vacuum. Simultaneously, they were measuring rainfall and logging temperatures.

Thomas Jefferson — The data keeper

Jefferson began what would become one of the most remarkable weather records in American history on July 1, 1776, and on July 4, he bought that new thermometer.

He was in Philadelphia as a Virginia delegate to the Second Continental Congress, in the middle of shepherding the Declaration of Independence toward its adoption. On July 4, he woke to a cool 68 degrees at 6 a.m., climbing to 76 by early afternoon. We know what the temperature was on July 4 because Jefferson wrote it down, as he did for nearly every day of his adult life. He maintained his meteorological record, with some gaps, until late June 1826, just days before his death.

His entries were meticulous. He generally made two observations a day, one at sunrise when he believed temperatures would be at their lowest, and another around 3 or 4 in the afternoon to capture the daily high.

He recorded temperature, barometric pressure, wind direction, precipitation, and what he called "indexes of climate" such as the first appearance of certain birds in spring or the blooming of trees. In 1784, he wrote to his friend James Madison urging him to keep a weather diary of his own, laying out exactly how it should be organized.

Jefferson wasn't doing this casually. He envisioned a national network of weather observers who could collectively build a reliable picture of the American climate, describing what it would require as years of "steady attention to the thermometer, to the plants growing there, the times of their leafing and flowering, its animal inhabitants, beast, birds, reptiles and insects; its prevalent winds, quantities of rain and snow, temperature of mountains, and other indexes of climate."

It would take nearly a century for that vision to be realized. The United States Weather Bureau, forerunner of today's National Weather Service, was established in 1870, but the impulse behind it traced directly back to Jefferson and his contemporaries.

George Washington — The strategist

For Washington, weather was a working concern. As a surveyor, soldier and farmer, he needed to know what the sky was going to do, and he kept a record of it in his diaries for most of his life, separate from his other entries.

The daily observations gave him a rough weather indicator for his farm plans at Mount Vernon. His final diary entry, written on Dec. 13, 1799, the day before he died, was a weather note: "Morning Snowing & abt. 3 Inches deep. Wind at No. Et. & Mer. at 30. Contg. Snowing till 1 Oclock and abt. 4 it became perfectly clear."

His most famous weather instrument was a weathervane he designed himself, commissioning Philadelphia artisan Joseph Rakestraw to build a dove carrying an olive branch in its beak.

He told Rakestraw he "should like to have a bird ... with an olive branch in its Mouth."

Installed atop the Mount Vernon mansion in the fall of 1787, the Dove of Peace symbolized Washington's hope for the new nation. It was also a practical tool: wind direction told an 18th century farmer a great deal about the weather to come.

What set Washington apart from Jefferson was how he put his weather knowledge to use.

Jefferson was building a scientific record. Washington was making decisions.

The fog at Brooklyn, the nor'easter at the Delaware, the squall at Yorktown: He had spent a lifetime reading the sky on the farms and survey lines of Virginia, and that instinct served him well when the stakes were highest.

Benjamin Franklin — The pioneer

If Jefferson was the data keeper and Washington was the strategist, Franklin was a genuine weather scientist, arguably America's first.

His curiosity went far beyond the famous 1752 kite experiment that demonstrated lightning was electrical. As early as 1743, he was comparing weather observations in letters from friends in other colonies, becoming one of the first to recognize that North American storms tend to move from west to east and that a storm's course could be plotted.

He published some of the first recorded weather forecasts in his Poor Richard's Almanac. On a 1775 voyage to England, he lowered a thermometer into the Atlantic, found the Gulf Stream ran six degrees warmer than the surrounding sea, and used the data to produce the first scientific chart of the current.

He even connected the brutal winter of 1783-84 to a volcanic eruption in Iceland that summer, one of the earliest attempts to tie a specific weather event to an atmospheric cause.

His curiosity could be reckless. When Franklin spotted a small whirlwind spinning down a Maryland road, he galloped alongside it on horseback, striking it with his whip to see if he could break it apart.

That same relentlessness drove decades of work mapping North American storm systems, and the Franklin Institute later established Pennsylvania's first meteorological station in his honor.

He was also raising concerns about human impact on the atmosphere long before anyone used the term.

According to Harvard historian Joyce Chaplin, Franklin redesigned his stoves to reburn their own smoke, described early notions of urban "microclimates," and he opposed the rampant deforestation of the colonies, worried that clearing too many trees might permanently alter the weather.

Chaplin considers Franklin an architect of modern climate science.

He died in 1790, long before meteorology became a formal discipline, but the questions he raised about human impact on the environment are the ones scientists are still working on today. He lived by his own line from Poor Richard's: "Some are weatherwise; some are otherwise."

A tradition as old as the republic

The founders worked with glass thermometers, brass weathervanes and quill pens, but the instinct behind their record-keeping runs straight to the present day.

Jefferson's dream of a unified network of weather watchers eventually became the National Weather Service. Franklin's ocean temperature logs helped lay the groundwork for oceanography. Washington's journals gave us some of the earliest baseline data we have for the American climate.

We know the midday temperature in Philadelphia on the first Fourth of July was a comfortable 76 degrees, not because of a government archive, but because Thomas Jefferson stepped outside to check his thermometer in the middle of founding a country. So when you glance at the radar before heading out to the fireworks this year, you're keeping up a habit as old as the republic itself.