Minnesota (Fort Snelling) weather for the year 1843

Coldest Year In History

The strange series of aberrant cold spells reached their most extreme extent during 1843, the coldest year in Twin Cities area history (annual mean temperature: 38 F) down to the present. February and March were a combined 20 F below average, late-May through mid-June equally backward as last year; Lake Pepin did not open until well into May. October set a mark for low average temperature that still stands today and November was just barely warmer than last year’s record setter. Total precipitation was about 24 inches.

The Most Drawn out Winter in History accompanied by Appearance of a Great Comet – The 1842-3 winter was easily the lengthiest in 24 years’ Post history up to this time. November’s exceptionally early and protracted cold would be followed by an even more amazing period of far below normal temperatures encompassing all of February and March. Anomalous cold in the same winter coming so early, only to return and persist so late has never been repeated to such a degree in the climatic record down to the present. One climatic researcher attributed this, possibly, to the effects of another volcanic dust veil [Rosendal, 1970], not unlike that of 1835. In addition to the unusual meteorological goings-on, a large comet, described in detail, was viewed over the last half of March. Register entries were not made over the first ten days of January as Surgeon George Turner evidently awaited a new thermometer, part of a military revamping this year of its weather observing practices. Temperatures were now to be taken at Sunrise, 9AM, 3PM, and 9PM, employing a standard instrument manufactured by George Tagliabue of New York City [National Archives, 1981]. Detailed instructions on how to make the observations were issued: “the standard thermometer should be in the shade, in the free air, on the north side of a large tree, uninfluenced by reflected heat from any source, [as] confined air will affect it injuriously”. Among other changes, wind speeds were to be estimated quantitatively, using a hierarchy of forces from 1 to 10; sky cover similarly evaluated utilizing a “Clearness of the Sky” scale from 0 to 10. Observations for January 1-10 at Fort Crawford indicated some occasionally bitter weather in that vicinity, several mornings around -20 F, conditions at least that severe likely to have been felt upriver. The first Snelling readings on the 11th-12th caught the tail-end of a cold snap, -12 F and -18 F read, respectively. Conditions changed dramatically over the next week. The 16th-20th was thawing almost continuously, accompanied by fog, mist, and 1/2 inch of rain and snow mixed. The next eleven days were seasonable to mild, afternoons generally in the mid-20’s to 30’s, but a sharp cold wave on the night of the 30th brought temperatures in the -4 F to -6 F range for all of the 31st. Outdoor conditions were decidedly dangerous with northwesterly winds estimated at Force 6 (45 miles per hour). This introduced the most remarkable of the early ’40’s cold spells, a 60-day period through 1 April with near or below zero temperature nearly every morning, and not a single temperature through 31 March reaching 32 F. February (mean temperature: 1 F), second coldest calendar month since ’20, had zero or colder temperatures on 20 days, precipitation consisting of 15 inches’ snow. Through the 18th, just three afternoons got as high as warm as 10 F, the month’s two coldest mornings (both -23 F) felt on the 7th and 17th. Several afternoons over the last ten reached the mid-to-high 20’s, the 20th hitting 30 F, but following a “violent snowstorm” on the 26th, leaving five inches, bitter arctic cold set upon the area again. The 27th and 28th each failed to reach as high as zero, and minus 20 F was recorded on the morning of the latter. March (mean temperature: 4 F) provided the most aberrantly cold individual calendar month in the entire climatic history down to the present, an incredible 27 F below average, more than 4 standard deviations! Just 10 percent of the Januarys, 3 percent of the Februarys and 1 percent of the Decembers since 1820 have been colder! In spite of the steadily advancing sun angle and frequent sunny days, temperatures failed to reach 32 F all month, 24 days having at least one observation at zero or colder. Total snowfall was about 8 inches. The month opened with four successive mornings below -10 F, including -20 F on the 2nd, a tie for month’s lowest. Warming associated with approach of a snowstorm that would drop 3 inches brought 27 F on the 7th, a tie for month’s highest, but a cold wave after its passage brought -17 F by next morning. Following another snowstorm that left 4 inches on the 10th, the mercury in its wake sank to -20 F on the morning of 13th. Bright but steadily cold weather prevailed through the close, subzero temperatures felt most every morning, afternoons seldom rising out of the teens. Fifteen below was registered as late as the 26th, -11 F on the 30th. Several additional light dustings of snow brought the ’42-’43 snow season’s final total to 40-45 inches, not including those accumulations that might have come in early January. As extraordinary March’s weather was, it did not receive any particular mention in the register, that being reserved for a memorable astronomical occurrence that became visible after mid-month — The Great Comet of 1843. This object, noteworthy for its extremely long tail and close passage to the sun, was reportedly visible during the daytime by some European observers. Its return is predicted for the year 2355 [Dauvillier, 1961]. Special notes were included by Surgeon Turner at month end: “This phenomenon which has been observed every night since the 15th from 7 1/2 PM until 9 1/4 PM except when the atmosphere has been unfavorable has an apparent inclination to the plane of the horizon on nearly 27 degrees, and its extent across the arch of the heavens is at least 30 degrees. The train at its most elevated point appears to the eye about 10 feet in breadth and gradually diminishes to about 2 feet, when it is last at an elevation of 5 degrees above the horizon. The light emitted from the immense shaft is pale but distinct. The general bearing is SW. The Comet has not been previously observed. These remarks are the most important I can furnish as I have not the means (even if I had the ability) further to investigate this most interesting phenomenon”.

Rapid Warmup in April but a Backward May – April brought a rapid return to relative seasonableness. Monthly mean temperature (43 F) was only slightly below average, 0.75 inches of precipitation falling on five days. The 1st was cold with a daily range of 1 F to 32 F, this, however, the first thawing day of the last sixty. Gradually warmer temperatures followed, 42 F reached on the 5th (“thaws rapidly in the sun”), 49 F on the 7th, 58 F on the 11th and 66 F on the 13th. Most subsequent afternoons were in the 50’s and 60’s, a notable exception being 79 F on the 28th, the monthly maximum. Spring’s forward pace was much slower in May, a very cool and cloudy month. Mean temperature (51 F) was only 1 F higher than last year’s low standard, rain falling on 13 days to 3.16 inches. Highest 3PM temperature was only 72 F, lowest such May monthly maximum of the Snelling era. Each of the first eight mornings were in the 30’s, the 4th and 5th especially unpleasant with readings for both hovering in the 30’s night and day with occasional gale-force northeasterlies. The 6th also reported snow and rain mixed, the 16th only 33 F at sunrise. Lake Pepin, incredibly, did not open until the 20th [Ludlum, 1968].

Backward Early June, Cool/Pleasant July & August – June (mean temperature: 63 F) was very cool over the first half, very warm and humid over the last third. Rains were frequent and plentiful, 5.22 inches totaled on 15 days. The first 16 days were strikingly similar to last year with exceptionally cool temperatures, overcast skies, and frequent showers. Afternoon temperatures were almost exclusively in the 50’s and 60’s, roughly half the mornings in the 30’s and 40’s. The 6th was only 35 F at sunrise. On the 17th, a several day stretch of south to southeasterly winds introduced the season’s first warm and muggy spell. Diurnal ranges on the 20th and 21st were each 74 F to 86 F, the 26th’s 68 F to 89 F. Six rains over the last ten days dropped 2.78 inches. Perhaps it was during this wet month that the great log boom at Stillwater reportedly broke, “the cutting of logs of the whole winter floated down the Mississippi” [Ford & Johnson, 1961]. July (mean temperature: 70 F) was generally pleasant with only a few hot days and relatively light rainfall (total: 2.09 inches on seven days). Following an opening-day thunderstorm that left 1.10 inches, a long dry and cool pattern set in to prevail through the third week. Just 0.07 inches fell over the interval, most afternoons in the 70’s. The last ten were warmer and wetter, most days in the mid-80’s to as high as 90 F, evenings in the mid-to-upper 60’s. A shower on the 27th left 0.85 inches. August (mean temperature: 67 F) featured a remarkably uniform day-to-day temperature pattern, most afternoons in the mid-to-upper 70’s, nights in the upper 50’s to low 60’s. Rain fell on 8 days to 1.84 inches. Just two afternoons broke 80 F, the warmest 81 F, another coolest monthly extreme maximum record. Sixteen mornings were foggy.

Rainy September, Exceptionally Cold October/November – Fall was not without its share of abnormal temperatures. A relatively seasonable (but wet) September was succeeded by the coldest October/November period in local climatological history down to the present. September (mean temperature: 58 F; 5.14 inches of rain), like so many other past years opened with a one-week extension of summer, most afternoons in the mid-70’s to low 80’s, nights in the upper 50’s or higher. Strong northwesterly winds at the start of the second, however, brought the season’s first autumn chill. Several successive nights dropped into the high 30’s to low 40’s, the afternoons holding in the 50’s and 60’s. Showery weather with changeable temperatures made up the rest of the month, nearly 4 inches’ rain received. Gale-force south-southwesterly winds brought 84 F on the 20th, but autumn was definitely in control over the last week, nearly every morning in the 30’s and 40’s, afternoons in the 40’s and 50’s. The mercury was 32 F at sunrise of the 26th. Aberrant cold returned again for most of October, monthly mean temperature (36 F) the lowest ever recorded for this month locally. Precipitation totaled .50 inches, about half of this melted snow. The first week had a few pleasant days, the 5th recording 70 F, the month’s warmest. But just two days later readings were in the mid-30’s all day with grey, dreary skies. Few afternoons got warmer than the mid-40’s thereafter, nearly every morning freezing. The 28th was only 23 F at 3PM, with the 29th and 30th, respectively, 11 F and 10 F at sunrise. November brought more unseasonable, steady cold. Monthly mean temperature was just 26 F. Afternoon readings broke 40 F just once, many days spent around the freezing mark with dreary, overcast skies. Adding to the general cheerlessness, a sleetstorm on the 14th-15th dropped .23 inches’ water content, another heavier .90 inch storm with “snow, rain, & hail” commencing less than 48 hours later. The last week was sunnier but continuously below freezing, the mercury 5 F on the 30th for the month’s coldest temperature.

Dreary but Mild December – December was little different than November with more grey, dark, and dismal weather. Monthly mean temperature (22 F), however, was the mildest in ten years, average clearness of the sky 3.6 (compared to November’s 4.1). Week one was the chilliest, -2 F read on the 5th, the month’s lowest. Several light snows dropped 2-3 inches. Mild, overcast, and virtually snowless weather made up the remainder, most afternoons in the high 20’s to low 30’s, the month’s warmest (39 F) coming on the 10th. New Year’s Eve was “raining this morning”, start of a heavy rain and sleet storm that would carry over into the first days of 1844.