Minnesota Weather Summary for the 1860’s
Coldest Decade in History, Precipitation Extremes.
Anomalously cool temperatures, particularly during the summers, with precipitation extremes, both droughts and deluges, featured the 1860’s’ weather in Minnesota. The long-term cooling trend having reached its lowest, average temperature for the decade, 41 F, using St. Paul Smithsonian records, was the coolest of any of the five thus far, but also the coolest of any of the thirteen since. To those that lived through it, however, the most memorable meteorological features were probably the precipitation extremes. A protracted drought gripped the State from Fall 1862 through early Summer 1865, abruptly followed by torrential rains over much of the remaining 1865 summer. Additional, extraordinarily heavy rains came over June/July 1867 and August/September 1869. Counting the heavy snowfall induced spring runoffs of 1861, 1862, and 1866 (the latter affecting outstate areas primarily) there were more high water and flooding episodes during the 1860’s (five) than all the other previous four decades combined. The 1862-65 drought was the worst since the arrival of whites, raising questions about the nature of the climate here, in addition to causing low-river-stage problems that hindered the export of wheat surplus by steamboat.
Thermal anomaly-wise, this was the decade of cool summers, average temperature of the Junes, Julys and Augusts in St. Paul just 67 F, nearly 4 F colder than the modern day normal and 3 F lower than those of the 1850’s at Fort Snelling. Ninety degree weather was a comparatively rare event during these summers, killing frosts felt in both July and August 1863. Other reports of frost from outstate areas came in August 1860, June 1864, and June and August 1866 . A major exception to this was the hot July of 1868, the warmest since July 1830. This was followed just two months later, though, by the coolest September in recorded history down to the present. Other thermal comparisons with the 1850’s had the 1860’s’ winters 1 F warmer, the springs 1 F colder, and the falls 2 F colder.