Minnesota (Fort Snelling) weather for the year 1841
Premature Spring Heat, Very Cold Early Autumn (graphic)
Weather anomaly patterns for 1841 were somewhat similar to those of 1840. Winter was mild with scarce snowfall (at least through the equinox) and late spring brought an extended period of unseasonably early heat. Fall provided more premature cold, this year’s installment, however, much more anomalous than 1840’s, covering nearly all of September and much of October. The latter was the first in a series of exceptionally unseasonable cold terms, covering multiple weeks at a time, which would occur during each of the next three years – at least some of the fall months would be affected each time. Annual mean temperature for 1841 was 44 F, total precipitation 25 inches. More than 9 inches of the latter, however, fell from just two storms in September, most of the other portions of the year precipitation-deficient.
Another Mild Winter, but Late Heavy Snow – Aside from some scattered cold periods and a big snowstorm in late March, general weather conditions over the first three months of 1841 were very similar to last year — mild and relatively snowless. January (mean temperature: 12 F) featured a couple of abbreviated arctic spells, snowfall totaling about 2-3 inches. Week one brought the winter’s first really bitter weather, three successive mornings in the –12 F to -20 F range, but warmer weather followed, temperatures reaching thawing levels by the middle of the second. A new, more intense arctic outbreak brought -32 F on the 17th, -20 F recorded the following morning, but the month finished very mild. Nine of the last ten days reached the 30’s and 40’s, including 46 F at sunset of the 23rd (“P. M.” readings absent this month). February (mean temperature: 17 F) had a cold first half but very balmy second, snowfall totaling about 2-3 inches again. The first two weeks were the winter’s coldest extended period, the spell being introduced by a cold wave on the 2nd which plummeted the mercury 37 F in 24 hours to -7 F by sunrise of the 3rd. Seven of the next nine mornings were below zero also, as cold as minus 12 F. But conditions after the 15th turned very balmy again with afternoon readings in the 40’s on roughly half the days. The 20th soared to 54 F and the 22nd 60 F, the latter highest wintertime (December-February) reading of the entire 1820-58 Fort Snelling era. March (mean temperature: 33 F) continued unseasonably mild, almost every afternoon after the first week in the 40’s or warmer. Fifteen of the first twenty days were “fair”. Two to three inches’ snow fell on the 14th, the month’s first precipitation, but this quickly melted as much warmer weather followed. The 18th reached 62 F and the 19th 59 F. Cloudier, wetter, but still mild conditions closed the month, several light rains leaving 0.20 inch, the 28th-29th bringing a surprise 10-inch fall of heavy, wet snow. No notes appeared this month or next regarding river openings.
Backward April but Premature Heat after mid-May – Spring’s pace of warming this year was more irregular then last, unseasonable cold displayed over much of April, a return visit of premature summery heat, however, coming in May. The former (mean temperature: 40 F – 1.40 inches’ precipitation) was about as cool as 1837, just one afternoon warmer than 44 F over the first two weeks, almost every night freezing. A couple of one-inch snows also fell over the period. A modest warming trend brought 68 F on the 22nd, highest of the month, but conditions then relapsed again, the 25th recording 0.75 inches’ cold rain with temperatures hovering in the mid-30’s. The 29th was similarly disagreeable with 0.32 inches’ rain/snow mixed and 29 F at mid-afternoon. This latter snow extended the 1840-41 snow season’s length to six months and 27 days, a record; total accumulation for the season finished around 40 inches. The cool spell climaxed over the first days of May with 23 F at sunrise of the 2nd, this the season’s “last freeze”. Afternoon temperature this day was only 41 F. From here, afternoon readings gradually warmed day-by-day, the 50’s reached by the end of the first week with the 60’s being general by week two. After mid-month, conditions warmed considerably, taking on a strong resemblance to last year’s anomalous heat about this time. Four straight days in the mid-80’s were felt over the 17th-20th, morning readings in the low-to-mid-60’s. Following a slight cooling, the 86 F-88 F range was attained on three of the last five afternoons. Monthly mean temperature finished at 60 F, total rainfall 1.50 inches. June (mean temperature: 70 F) was several degrees above normal with more normal rainfall, 4.24 inches on eight days. Temperatures continued unseasonably warm and humid over the first eleven, five afternoons reaching 88 F to 92 F, virtually every night in the 60’s. The 10th and 11th were especially muggy, sunrise temperatures at 70 F and 74 F, respectively. A strong cold front with thunderstorms on the night of the 11th-12th finally broke the spell, the succeeding afternoon just 66 F in the “P. M”, some 26 F cooler than 24 hours’ previous. Mostly cloudy and cool weather prevailed over the next two weeks, nearly every afternoon in the 60’s to 70’s, one morning as cool as 50 F. Warm and humid weather was back at the close, 88 F and 90 F recorded on the 27th and 28th, the last two mornings 74 F and 70 F, respectively, at sunrise. Phenological notes had strawberries “ripe” on the 12th and “abundant” on the 18th.
Pleasant Summer – Similar to a year ago, May and June’s early heat did not presage an oppressive July or August. The former (mean temperature: 73 F) was only seasonable in temperature with light rainfall – 1.47 inches on three falls. The first two weeks were pleasant, nights mostly in the mid-60’s and afternoons generally in the mid-to-high 70’s. Two thunderstorms, the only ones of the month, dropped 1.37 inches during the second week. An abbreviated heat wave set in during the third week and into the fourth, four out of five afternoons over the 19th-23rd between 90 F and 93 F. Morning readings over the 20th-24th ranged from 70 F to 76 F, but only two afternoons thereafter got as warm as 84 F, one morning dipping to 53 F. August (mean temperature: 68 F) was also generally pleasant in temperature with continued light rainfall, 1.17 inches on five falls. There were no 90’s, the highest a comparatively moderate 86 F. Most afternoons over the first two weeks were in the 70’s, with a couple of mornings in the low 50’s. A brief humid term was experienced during the third week, three “A. M.” readings in a row noted in the 70’s, the “A. M.” of the 22nd, however, 48 F. The last week had a couple of afternoons confined to around 60 F with cloudy skies and northerly winds, but start of a late-season heat wave that would carry over into the early days of next month, the 31st reached 85 F.
Extraordinarily Cold/Wet Early Fall – September (mean temperature: 54 F, coldest in 22 years) brought the first of a series of extraordinary and extended below normal temperatures spells that would set in at scattered intervals over the next several years. Unseasonable heat, however, predominated early, 90 F to 92 F readings recorded on the 4th, 5th, and 6th. Following .15 inches’ rain on the evening of the latter, though, an exceptionally strong cold front, almost winter-like in intensity, swept through, bringing mid-autumn-like temperatures in the space of a few hours. Next afternoon, the mercury stood at just 51 F, 39 F lower than 24 hours’ previous, the following sunrise [of the 8th] 40 F. Afternoon temperatures displayed a gradual up-trend over the next week, 72 F reached on the 14th, but another cold spell then set in, the next eight days exceptionally chilly for mid-September with no afternoons readings higher than 50 F. Only one afternoon reached as warm as 60 F over the whole rest of the month, numerous nights dropping into the 30’s; the 17th was 32 F at sunrise. Adding to the general unpleasantness, a heavy rainstorm dropped 3.05 inches on the 19th, another series of storms over the 25th-27th drenching the Post with 6.10 inches more. Possibly about this time, a steamboat “pleasure excursion” was taken up the St. Peter’s River as far as Shakopee, a rare event in this era [Williams, 1881]. October (mean temperature: 45 F) was also unseasonably cold over its greater part. A strong warming trend, however, closed the last several days. Total precipitation was 1.55 inches on seven falls. Temperatures remained unseasonably cool well into the second week, afternnon readings almost exclusively in the 50’s, nighttime temperatures dropping into the high 30’s to mid-40’s. The mercury finally reached 70 F on the afternoon of 14th, highest in 30 days, but next day a strong cold front ushered in a new extended period of unseasonable coolness, afternoon temperatures over the 16th to 27th no warmer than the high 40’s, mornings freezing almost each day. The first snow of the season dropped an inch on the 23rd, the mercury just 27 F next afternoon. The month’s warmest weather came over the last three days, daily temperature ranges in the mid-50’s for the mornings to the mid-60’s for the afternoons.
More Seasonable Weather in November and December – November (mean temperature: 31 F) had mostly seasonable to mild temperatures and sunny skies. Total precipitation was 0.84 inches on four days. Uniformly mild temperatures prevailed over the first three weeks, afternoon temperatures typically in the 40’s and 50’s, just two mornings lower than 20 F. The month’s highest temperatures came on the 9th and 10th with 60 F and 62 F, respectively. Temperatures cooled over the last week, but not to extremely cold levels, afternoons confined exclusively to the 20’s, one morning 2 F. December (mean temperature: 21 F) was relatively mild with increasing snows after mid-month. Temperatures recovered to balmy levels on the 1st (46 F), ten of the first 14 days thawing as well. Moderate showers totaling .20 inch came on the 12th. After a 5-inch snowstorm on the 14th, though, a colder trend developed. Afternoon temperatures through the close were generally restricted to the teens and 20’s, overnight temperatures mostly in single figures. Three additional snows left about 7-8 inches, resulting in a respectable depth at year’s end.