There’s nothing quite so dreary as a cold rain on Independence Day. Just imagine how cranky people would be after 30 years of bad weather.

That’s exactly what colonists endured in the three decades leading up to the American Revolution, according to a retired University of Maine professor and a colleague at Northern Arizona University.

“There might not have been a revolution if the weather was better,” said David Smith, emeritus professor of history and cooperating professor of quaternary studies at the University of Maine.

Smith and William R. Baron, now an associate professor of history and quaternary studies at Northern Arizona, have been collecting old weather records since the mid-1970s. From the casual jottings of New England farmers to the methodical observations of Harvard-trained ministers, the academics have compiled 27,800 records of weather between 1697 and 1947.

“It’s a discontinuous but massive record from a long time in the past,” said Smith.

Baron and Smith became interested in the relationships between weather and history just as the issue of global climate was becoming important. Their work has been supported by several National Science Foundation grants.

In their search for records, the two researchers visited 67 libraries and archives in New England. They found their earliest sources of information on college campuses. Yale, Bowdoin and Middlebury have records going back to the late 1700s or early 1800s, Smith said.

“Altogether, I suppose we have looked at 2,000 diaries, but we only relied on those of some real lengths,” said Smith.

Even more important were the records kept by students of Jonathan Winthrop, a respected Harvard professor of moral philosophy (physics) for almost 50 years in the 1700s.

According to Smith, Winthrop was convinced that weather data would be vital to future scholars. He taught all of his students to keep detailed records of precipitation, temperature, wind strength and direction, cloud cover and unusual events.

“Virtually everybody took his class at Harvard,” said Smith. “We found about 75 diaries kept by his students, all taken with scientific exactitude, some for as long as 50 years.”

The second in a series of reports on their findings has just been published by the Maine Agricultural and Forest Experiment Station. The bulletin, titled “Growing Season Parameter Reconstructions for New England Using Killing Frost Records, 1697-1947,” shows that early settlers faced a much harsher climate than current residents.

According to Smith, a worldwide phenomenon known as “the Little Ice Age” affected New England weather patterns from 1500 through about 1850. The weather was both colder and more variable, making agriculture a very risky business.

Unfortunately, it was the only business for most early settlers. They relied on farming to feed their families and perhaps generate a small surplus of hay or grain that could be traded for items that couldn’t be produced on the farm.

According to Smith and Baron, the weather was especially bad in the years just before the American Revolution. “During the 1740s through the 1770s, a combination of uniformly clear skies (some 20 percent clearer than today) and frequently fluctuating, cool then warm, springs and falls contributed to extreme fluctuations in growing seasons,” they wrote.

The researchers estimated that the New England corn crop was poor or nearly poor in 15 of the 37 years ending in 1776. The crop was rated good or better in only seven years.

“The timing of poor crop yield was highly significant to the coming of the Revolution,” wrote Smith and Baron. “Crop failures clustered in the years 1761 through 1764, just preceding the Stamp Act crisis, and in 1768 through 1772 (with the exception of 1769) during the period of unrest leading to the Coercive Acts. It does not take much imagination to perceive the mind-set of a New England farmer low on specie and/or a crop surplus for barter …”

The report is available from the publications office at the experiment station, Room 1, Winslow Hall, University of Maine, Orono 04473.