I see Chicago’s weather records as those officially observed since late 1870. Are there earlier records?
— Wayne Callham, Chicago
Chicago’s official weather records date back to Nov. 1, 1870, but there is a smattering of information from 1820 to 1836 when observations were taken at Fort Dearborn. A few observations were also taken at the Mechanics Institute in 1844, and nearly continuous readings were taken by Smithsonian observers from 1859 until late 1870, when the Army Signal Corps began documenting the city’s official weather history. Many of those early observations, which consisted mostly of temperature data, were compiled by professor Henry A. Hazen and published in his 1893 book “The Climate of Chicago.” Journals, diaries and newspapers also provide valuable insight.