From Jefferson's Thermometer to the Telegraph: How America Built Its Weather Record

Each month NOAA's National Centers for Environmental Information (NCEI) reports on the nation's climate: a winter 1.8°F above average, record rain in the Mississippi Valley, an April 2.2°F below the 20th-century average, the 13th coldest on record. Businesses, governments and the public rely on those reports. Behind them is a record going back almost 125 years, to 1895. Where did it come from?

Average April temperatures (1981–2010) compared with April 2018. NOAA Climate.gov, from NCEI data.

The first observers

The earliest known systematic weather observations in America were made by John Campanius Holm along the Delaware River in the 1640s. Early presidents kept records too. Thomas Jefferson bought his first thermometer while writing the Declaration of Independence and his first barometer a few days after it was signed, and kept an almost unbroken weather record until 1816. George Washington made his last weather entry in his diary the day before he died.

Networks grew through the 1800s. In 1818 the Army's Surgeon General told his surgeons to record the weather and everything about the climate, terrain and diseases around their posts, to learn whether climate affected soldiers' health and whether a district's climate changed over time.

The telegraph

The telegraph, working from 1845, changed everything: observations from far away could be gathered, plotted and analysed in one place, and storms could be forecast by telegraphing ahead. Volunteers recruited through a circular in the press were sending reports to the newly founded Smithsonian Institution, more than 100 of them by the end of 1849; by 1860 several hundred stations sent daily telegraphed reports to the Washington Evening Star.

Telegraph-reporting weather stations as of December 1849, reporting to the Smithsonian. NOAA Climate.gov, from NCEI historical data.

After the Civil War, the need to warn sailors of storms led Congress in 1870 to have the Secretary of War take observations at military posts and warn of storms on the Great Lakes and the Atlantic and Gulf coasts, extended nationwide in 1872 for commerce and farming. The Army's Signal Service grew from 24 stations in 1870 to 284 in 1878, each observing at least three times a day: pressure, temperature, precipitation, humidity, wind, clouds and the state of the weather. In 1890 Congress moved the work to a civilian Weather Bureau in the Department of Agriculture, the ancestor of today's National Weather Service.

San Diego’s long rainfall record, stitched together from Army observations through to today’s airport station. NOAA Climate.gov, from NCEI data.

The Cooperative Observer Program

The modern record really begins in 1890, when Congress also created the Cooperative Observer Program (COOP). For more than 120 years it has enlisted volunteers to record daily temperature, precipitation and snow, and sometimes evaporation and soil temperature. By 1895 there were more than 2,000 COOP stations across the contiguous United States, some in territories not yet states, and as far back as the 1890s there were stations as remote as Hawaii and Alaska.

Cooperative observer locations, decade by decade, 1890–2009. NOAA Climate.gov, from NCEI data.

The program has always depended on volunteers, and in many families the duty has passed down the generations. Today each of the 122 National Weather Service forecast offices recruits, trains and equips observers. Until the 1990s observers wrote each day's readings on paper forms and mailed them in at month's end, so a month's climate record was not ready until months later. Now they send their readings online every day, feeding forecasts and warnings and NCEI's picture of a changing climate.

A cooperative observer’s paper form from Royal Palms, Florida, December 1982. NOAA, courtesy NCEI.

Where the old records went

The observations are kept in NCEI's Global Historical Climatology Network–Daily, which includes stations around the world. And the readings from the early and late 1800s? They form the U.S. Forts record, though not all were taken at forts, digitized in NOAA's Climate Database Modernization Program; some are already in the daily network, with hundreds more to come.

Sources

• NOAA Climate.gov, "Thomas Jefferson and the telegraph: highlights of the U.S. weather observer program"; rewritten in hubnx's own words. Maps and graphics: NOAA Climate.gov and NCEI.