Minnesota (Fort Snelling) weather for the year 1838

Temperature Extremes, Wet Summer

Extreme temperature events and spells, mostly cold, predominated Fort Snelling’s weather during 1838. Annual mean temperature was 42 F, tying 1831 and 1836 for lowest to date, even though summer (June-August) equaled 1823 for warmest so far (73 F). Annual precipitation was 29 inches. Except for a record warm March, January through May were all well below normal. A long arctic spell in February brought the coldest temperature yet observed here: -40 F. July through September, though, were all much warmer than usual; eleven inches’ rain was also recorded in July for the greatest single calendar month total of the 1820-58 Snelling era. October, November, and December, however, were each decidedly colder than normal, an unusual sequence, climatologically, for these summer to winter transition months. The Mississippi froze over for the winter during November’s second week, the earliest such event of the entire Snelling period.

Two Cold Terms and A Record Cold Night – Two prolonged arctic spells, one in January the other in February, marked the New Year’s side of the ’37-’38 winter. January (mean temperature: 9 F) came in with a heavy thaw over the first three days, temperatures hovering night and day in the high 30’s to low 40’s with occasional light rain. A brief cold snap brought minus 20 on the morning of the 10th, but a gradual warming trend then followed, 46 F reached on the 16th. Thereafter, arctic weather ruled, twelve of the last fourteen days with at least one minus 10 F or colder reading, the 31st dipping to -21 F for the month’s lowest temperature. February (mean temperature: 5 F) brought a brief return of thawing weather over the first week, several afternoons reaching the mid-30’s, but a cold wave on the 7th plummeted the temperature 42 F in just 17 hours to minus 8 F by next sunrise. On the 13th, an even colder blast descended over the area, -32 F read that morning, tying the absolute lowest mark set in 1821 and 1834. This standard would be short-lived, however, as the very next night, -40 F was read at 2AM on the Post thermometer, the mercury column “believed to have frozen”. The 15th was extremely cold also with -29 F registered at daybreak. A heavy snowstorm closed the month, 7 to 8 inches left over the three-day period 27 February to March 1.

Very Mild Start to Spring, Then Unseasonable Cold – Spring brought early forwardness (March), followed by a backward April and May, the latter month with a severe freeze well past mid-month. Mean temperature for March (39 F) was the highest thus far in nineteen years’ history. Precipitation was just 1-2 inches’ snow from three falls; total accumulation for the ’37-’38 season finished around 30 inches. Most afternoons over the first three weeks reached the 40’s and 50’s, the final six, however, more like early June, with afternoons consistently in the low to mid-70’s, morning readings in the mid-to-upper-40’s. On the 30th, the mercury rose to 76 F to surpass 1832’s mark by 2 F for the highest March temperature yet recorded. Similar to 1837’s cold turn between February and March, a similar March to April reversal occurred this year. The latter (mean temperature: 43 F) was just 4 F degrees warmer, the smallest spread between these two months in the entire climatic history down to the present. Precipitation was 2.41 inches, nearly 2 inches of this over the last six days. Most afternoons after the first week only reached the 40’s and 50’s, freezing or near freezing mornings occurring most every morning through the close. A noteworthy exception was 81 F on the afternoon of the 21st, the mercury, however, just 49 F at the same hour next day. May (mean temperature: 54 F) brought freezing or near-freezing temperatures almost daily into the second week, a major killing-frost event following past mid-month. Total rainfall was 3.05 inches on ten days. The early part was quite cool, morning temperatures over the 4th-8th ranging from the low to mid-30’s, afternoons no warmer than the low to mid-50’s. A warming trend set in around mid-month, low 80’s readings experienced on the 13th-15th, a summery 92 F recorded on the 19th – a warmest-ever-so-early-in-the-season mark. In a remarkable change, however, the 21st brought “high” north/northwest winds all day with snow reportedly seen in the afternoon. Next morning, the hardest freeze ever felt so late in the season at Snelling was perhaps experienced, the mercury 30 F at sunrise. Diary notes reported: “a piece of ice an inch thickness observed in [..shade?..] exposed to the sun in the parade at 11 o’clock AM on 22 May”. Sunrise temperature readings the next two days were near freezing as well, most of the month’s remaining mornings around 40 F.

Record Hot Summer, Heavy July Rains – Summer brought a dramatic warming, average temperature for June-August (73 F) equaling 1823’s high mark for the season. Accompanying the hot temperatures were regular and at times heavy rains. June (mean temperature: 72 F), warmest since 1829, had 4.76 inches’ rain on eleven days. Moderate temperatures characterized the first week, afternoons in the mid-70’s to low 80’s, nights in the 50’s. But the 10th rose to 93 F, and a week-long hot spell set in over the 16th-22nd, with continuously south quarter winds and afternoon temperatures between 89 F and 96 F. The Post was drenched over the last five days of the month with 2.80 inches’ rain. July was very warm with heavy rains, monthly mean temperature (77 F) the second highest figure of the Snelling era. Fifteen afternoons reached the nineties, nine days having rains that totaled 11.31 inches. On the 7th, the mercury climbed to 100 F, tying 10 June 1823’s mark for warmest reading to date, the “evening” reading still 86 F. An approaching cool front triggered a 5.10 deluge next day, however, and the prevailing northwesterly winds after its passage held the mercury at 76 F for the afternoon of the 10th. But another oppressive spell then began to build, the mercury hitting 98 F on the 15th. On this day, the Steamboat “Palyrma” docked, bringing news from Washington concerning ratification of the Indian Treaties of a year ago. White settlers were now free to lay claim to coveted lands in the St. Croix River vicinity and other places [Lass, 1976]. Another series of rains dropped almost 4 inches of rain over this and the next three days, an additional wet spell on the 27th-30th bringing 2.30 inches more. August (mean temperature: 74 F) tied 1833 for second warmest in 19 years. Rainfall totaled 3.58 inches on 11 days. The first half was warm but not exceptionally so, most afternoons in the mid-to-upper 80’s, two reaching 90 F. On the 19th, however, an unseasonably late hot spell set in, this and the next three days each reaching 92 F, the 26th climbing to 96 F for highest temperature ever recorded so late in the summer here.

Warm September, Unusually Persistent October-December Cold – The ’38 fall to winter transition featured lingering above average warmth in September but unusually persistent anomalous cold for October, November, and December. September (mean temperature: 62 F) equaled 1825 and 1833 as the warmest to date. Rain was light, just 0.71 inches on six falls. The first two days brought the coolest temperatures since late May, the 1st 44 F at daybreak and the 2nd 43 F at the same hour, but summery weather quickly returned, to predominate past mid-month. Afternoons frequently rose to the upper 70’s to low 80’s, nights generally remaining in the 50’s and 60’s. After some light rain on the 17th, just the second fall of the month, the season’s first extended autumnal spell set in, the 18th’s temperature range 38 F to 50 F, light frost reported on both the 23rd and 24th. Most other days through the close ranged from the 40’s in the mornings to the upper 60’s and low 70’s for the afternoons. October (mean temperature: 43 F) was cold, cloudy, but dry. Precipitation was 0.66 inches on four days. Mild to warm weather was felt over most of the first week, the majority of the mornings around 50 F, the 5th reaching 82 F in the afternoon. On the 6th, however, a sharp cold front swept through, the season’s first killing frost following next morning (32 F at sunrise). Repeat visits came on the 10th, 11th, and 12th. The rest of the month featured a remarkably persistent cold and cloudy pattern — stereotypical November weather a month early. Over the last twenty-one days, afternoon temperatures got no higher than the 40’s on every one but three, subfreezing temperatures felt on most nights, the coldest 21 F. Fifteen of the last eighteen days, also, were “Cloudy” in both the “A. M.” and “P. M.”. The season’s first snow, a 1 1/2 inch fall, came on the 17th. Alternating mean temperature anomalies or seasonal lag (above normal) persistence are the month-to-month norms for autumn and early winter in these parts, but in a most unusual succession given the time of the year, November and December each followed with much below normal cold as well. The former (mean temperature: 22 F) was the coldest in 20 years’ history, surpassing 1835’s mark by 2 full degrees F. All of the month’s precipitation was snow, totaling about 4-5 inches. The first three days brought a milder, brighter turn, afternoon temperatures reaching 52 F to 59 F under sunny skies. This was only a brief pause, however, as new unseasonably cold pattern immediately followed. The 5th was only 28 F at mid-afternoon, temperatures on the 8th and 9th, respectively, just 7 F and 2 F at sunrise. The Mississippi froze over on this latter day, earliest such recorded occurrence of the Snelling era. Bitter cold prevailed over the next nine days as well, minus 4 F recorded on the 17th for the month’s lowest temperature. A series of snows over the period also dropped about 4 inches. Much milder, more seasonable temperatures finally returned for the 19th-22nd, afternoons in the 40’s, but another cold snap over the last few days brought -1 F and 1 F readings, respectively, on the mornings of the 28th-29th. December (mean temperature: 10 F), coldest of the last seven years, displayed great day-to-day variation in temperature. Snow fell on nine days, total accumulation only 4-5 inches. Subzero cold was felt on 15 days, the coldest -19 F on the 27th. Gyrating day-to-day temperatures characterized the whole month, twenty-four hour temperature rises or falls of at least 25 F occurring eleven different times. The two warmest afternoons of the month, the 11th with 46 F and the 21st with 43 F were each followed by temperature descents of more than 40 F by next sunrise.