Minnesota Weather Summary for the 1840’s
Abnormal Cold Lapses, “Open” Winters.
Generally cool on an annual basis with progressively more snowless winters after 1844 characterized the 1840’s’ climatic conditions in the Fort Snelling vicinity.
The first half was marked by scattered but distinct far below normal temperature spells, persisting in some cases for more than two months at a time. Especially aberrant cold prevailed over most of September 1841, late-May to early July 1842, most of November 1842, February-March 1843, October-November 1843, and August through October 1844. Annual mean temperature for 1843 (38 F) still stands as the lowest in Minneapolis-St. Paul local climatic history down to the present, March of that year more than 25 F (and 4 standard deviations!) below normal. The 1844 frost-free season at Snelling was just 113 days long. A great two-year uptrend in annual mean temperature occurred from 1845 and 1846, the latter the warmest year until 1931, but 1847, 1848, and 1849 were all cool again, annual mean temperatures for each (42 F) tying for second lowest in Post history up to this time. Another noteworthy period of anomalous cold prevailed over July 1848 to January 1849, five of the seven months’ monthly means far below normal.
Like the previous two decades, nearly all the winters had light to moderate snowfall, the trend to lighter becoming especially so over the last half. Average amount at Snelling over ’45-’49 were less than half of the modern-day “normal”. Early summer of 1842 also had a drought-induced crop failure at Lac Qui Parle, Fall of that year with a 40-day precipitation-free spell at Fort Snelling. Growing season precipitation for the years 1844-9 averaged about normal at Snelling, the summer of 1849 having the first really damaging floods since 1826, with large quantities of logs being lost over St. Anthony Falls.