Minnesota (Fort Snelling) weather for the year 1842

More Cold Lapses

Temperature and precipitation extremes, both above and below normal, made up much of 1842’s weather at Fort Snelling, the most notable being two far below normal temperature terms covering late-Spring/early Summer and much of November. The incoming 1841-42 winter season was mostly mild and snow-free, March and April also showing a very forward seasonal advance, but after mid-May, conditions deteriorated drastically, extraordinarily unseasonable coolness felt all the way through early July. November also brought unprecedented early and severe cold. Annual mean temperature for the year (42 F) was a tie (with 1831 and 1836) for lowest thus far in the 23 years’ history. Annual precipitation was a respectable 25 inches, but like a year ago, a significant portion was concentrated over a short interval; in this case, more than 9 inches fell over mid-August to mid-September. October, however, was precipitation-free, encompassing part of a 40-day such spell.

Another Relatively Mild Winter – With a few exceptions, weather patterns for the balance of the ’41-’42 winter and early spring ’42 assumed the same mild and dry mode that had marked each of the last two years. January (mean temperature: 15 F), opened with a few near zero mornings and an eight-inch snowstorm on the 8th, but thereafter, a marked shift to mostly mild, sunny, and dry took place. During the second week, afternoon temperatures climbed to the 40’s several times, a January record-setting 49 F coming later on the 17th. Readings around 40 F were recorded on several additional afternoons over the final week. The only measurable snowfall after the early storm was a 1-2 inch accumulation over the 27th. February (mean temperature: 17 F) was similarly mild except for a few scattered bitter mornings over the middle portion. The mercury climbed to 46 F on the 2nd and 48 F on the 3rd, but following a 1-2 inch snowfall on the 7th, the winter’s coldest morning was felt the next morning with -22 F at sunrise. The next two weeks had a scattering of mornings with -10 F to -16 F temperatures. Mild and damp weather made up the closing week, several days near or above freezing for the entire 24 hours. A .20-inch mixture of rain and snow came on the 25th and another .40 inch of rain fell on the 28th. No additional snow to be received this season, the ’41-’42 winter’s accumulation finished at about 30 inches, nearly all of it having fallen over mid-December to early January.

Very Forward Early Spring – March (mean temperature: 38 F) was exceptionally mild, dry, and wind-free with 23 exclusively “fair” days and just one with precipitation, 0.44 inches’ rain on the 24th. Only four days had “high” winds, and except for a three-day spell during the second week with afternoon temperatures held confined to the mid-to-high 20’s, every day reached at least the 30’s. The first ducks were observed on the 5th, the first geese on the 8th. A record warm spell came after mid-month, the mercury soaring to 73 F on the 18th for highest ever experienced so early in the season here; unseasonable warmth was also felt on the 19th and 28th with 69 F readings on each. The “aments of the alder” were seen on the 25th, the “buds of the populus …[?]” on the 26th. April (mean temperature: 48 F) brought some needed rains, 2.07 inches falling over the first ten days, just .10 inch additional, though, over the remaining twenty. The river (Mississippi?) was reported clear of ice on the 6th. Temperatures were quite variable over the last three weeks. The mercury climbed to 73 F on the 11th, but dipped to 26 F on both the mornings of the 15th and 16th. The 19th-21st had 77 F, 81 F, and 86 F, respectively, the latter another highest-so-early-in-the-season mark. But the 25th and 26th were each no warmer than the 40’s at mid-afternoon, the 28th recording 26 F at sunrise with “ice and frost” noted. Diary notes reported “making gardens” on the 15th, and the arrivals of the steamboats “Amaranth” on the 21st and the “Galena” on the 29th.

Surprising Turn to Extraordinary Coolness- May, after mid-month, brought start of the decade’s next great unseasonable cold lapse, destined to last seven weeks into early July. Monthly mean temperature (51 F) finished just 3 F warmer than April, and set a new low mark for May. The first two-and-a-half weeks, however, continued much like April with sunny, dry weather and highly fluctuating temperatures. Nearly every day was “fair” at both the “A. M.” and “P. M.” observation times, and just one had rain. The 3rd and 4th were both freezing at sunrise, but a warming trend brought a summery 83 F on the afternoon of the 9th. Three days later, as the steamboat “Amaranth” arrived again, a cold rainstorm set in, .80 inches falling with temperatures hovering in the 40’s. The 17th brought “fair” weather, southwesterly winds, and 80 F in the afternoon, but overnight, high northerly winds and falling temperatures heralded the long spell’s onset, the 18th just 56 F at the mid-afternoon observation time. Most of the month’s remaining afternoons would be confined to the mid-50’s or colder accompanied by “cloudy” skies; the 29th was just 36 F at sunrise. Persistent damp chilliness continued almost uninterruptedly through all of June, by far the coolest month of its name in the entire climatic history down to the present; the 56 F monthly mean is more than three and a half standard deviations below average. Only eight afternoons got as warm as 70 F, 4.33 inches’ rain falling on 10 days. The 5th-19th was extraordinarily cool for the season, observed diurnal temperature ranges varying typically from the high 30’s/mid-40’s in the mornings to the high 50’s/low 60’s in the afternoons. Northeasterly or northwesterly winds predominated most every day. Back East about this time, snow flurries were noted on the 10th near Cleveland, snowfalls up to a half-foot recorded on the 10th-11th in upstate New York and Vermont [Ludlum, 1968]. A brief taste of seasonable warmth finally set in over the fourth week, three scattered afternoons reaching the 78 F to 81 F range, but the month closed with three successive afternoons in the low 60’s again. July (mean temperature: 67 F) repeated the performances of May and June with the coolest such month in 23 years’ history up to this point. Total rainfall was 1.78 inches, most of this from a single heavy fall during the first week. Just one afternoon higher than 70 F was recorded over the first eight days, three reaching no warmer than 60 F. Two of these latter days had high winds, one characterized as “stormy”. On the 5th, a 41 F temperature was read at sunrise, coldest July temperature of the Snelling era, and on the night of the 7th a heavy rain drenched the Post with 1.40 inches.

At Last, Summer – Summery conditions finally set in early of the second week, as a several day spell of “high” south to southeasterly winds brought the season’s first warm and humid weather. The 11th ranged from 68 F to 88 F, the 12th from 72 F to 90 F. A couple of brief cool spells followed, but over the 21st to 29th, a respectable nine-day warm and humid spell set in, southerly winds prevailing each day, diurnal temperature ranges typically in the high 60’s to the mid-to-upper 80’s. Following a 0.15 inch rain on the 28th, the first precipitation in three weeks, sharply colder weather moved in again, the 31st’s range just 48 F to 65 F. Sometime during the summer, perhaps this month, the lack of rain at Lac Qui Parle, several hundred miles up the St. Peter’s river, forced Thomas Williamson, a missionary-farmer, to relocate back to the Fort Snelling vicinity because of crop-failure [St. Paul Pioneer, 1865]. Later on, during the coming severe winter of 1842-1843, many of his Indian acquaintances would join him there [Hansen, 1958]. August (mean temperature: 68 F) was only moderately cooler than normal. Some 4.81 inches’ rain fell, but only on three days. Pleasant temperatures made up the first two weeks, daily ranges typically varying from the mid-to-high 50’s to the mid-70’s/low 80’s. No rain fell over the first fifteen days, but a decisive change came over the 16th-17th, as a prolonged rainstorm (“continued constantly for 24 hours”) dropped 3.15 inches. The last week was the month’s warmest, daily temperature ranges generally from the mid-60’s to the low to mid-80’s, another 1.66 inches of rain left.

Heavy September Rains Followed By October Drought – September (mean temperature: 57 F) brought additional heavy rains early in the month. The first two weeks had mostly cool days and mild nights, afternoons generally in the 60’s to low 70’s, nights frequently in the 50’s. The summer’s last warm and humid day came on the 10th, the daily range 66 F to 86 F. Through the close of the second week, nine additional rains totaling 4.73 inches fell, 9.54 having deluged the Post in 30 days since 16 August. Thereafter, just .10 inch additional was noted, this from a thundershower accompanied by a “tremendous thunderclap” on the night of the 25th. Morning temperatures dropped to the mid-30’s several times after mid-month, but no frost was reported. October (mean temperature: 48 F) was mild, windy, smoky, and devoid of precipitation. The season’s first freeze, a “heavy frost”, occurred on the morning of the 8th, but strong southwesterly winds brought 76 F on the 10th, the month’s warmest. A several-day stretch over the middle of the third week had afternoons confined to the 40’s, and the morning of the 19th dropped to 22 F (“ice this morning – the first noted”). The remaining 12 days swung back to classic Indian Summer weather: fair, “remarkably mild for the period of the year”, and smoky. The 23rd was 71 F, Halloween 67 F. Having taken fire on the 20th and “producing a smoky atmosphere”, the “surrounding prairies” would burn all the way through the first week of November.

Early, Prolonged Arctic Cold – November (mean temperature: 22 F) brought the year’s second extended spell of far below normal temperatures. The early part, however, carried over late October’s warmth and drought, south to southeasterly winds producing 67 F, 63 F, and 63 F readings on the first three afternoons, nighttimes holding in the mid-to-high 40’s. Signs of change began to appear on the night of the 4th, though, as the first precipitation in 40 days was received, 2.55 inches to fall over the next four days. Temperatures dipped below freezing for the first time on the 8th and three inches’ snow fell on the 9th, “the first of account this season”. Following five more days of dull, grey weather with temperatures hovering mostly in the 20’s, a powerful arctic front swept through, closing navigation the next day (the 15th) and plunging the mercury to minus 4 on the 16th. The remaining two weeks were like a mid-January cold spell, no observed temperatures warmer than 23 F, the mercury subzero or in single figures on ten of the fourteen mornings. On the 27th, -17 F was read at sunrise, recovering to only -6 F by 2PM. In spite of the balmy first week, November tied its 1838 namesake as the coldest in Post history up to this time, still sharing that distinction for the Twin Cities vicinity more than a century and a half later. Relative climatic normalcy returned in December, monthly mean temperature (17 F) more seasonable, but with virtually no precipitation, snow or rain, falling until the last week. Several straight days of mostly southerly winds brought the first thaw in nearly four weeks on the 3rd, 36 F recorded that afternoon. Subfreezing weather prevailed again over the next two, diurnal ranges typically in the teens to the low 20’s, several “scarcely perceptible” snows falling. High northerly winds on the night of the 21st-22nd dropped the mercury to -12 F by morning, coldest of the month. Gradually warmer weather followed as year-end approached. The 27th and 28th hovered near 32 F night and day, but the 29th was “snowing severely” with high winds and 6 inches of snow laid down. New Year’s Eve was 0 F at sunrise.