Minnesota (Fort Snelling area) Weather for the year 1821
Cold Winter and Spring, Uneven Summer Heat
Weather happenings were a bit less dramatic at Fort St. Anthony/Cantonment New Hope during 1821, with none of the tornadoes, freak early snowstorms, and sudden seasonal changeovers that had marked 1820. Annual mean temperature (43 F) was unchanged from a year ago, but Spring (March-May) was significantly cooler, and summer, especially the months of June and August, hotter, the latter one of the warmest Augusts in the entire local climatic record down to the present. Bitter weather was prominent again from the start of the year through mid-February and December brought a second straight year of premature arctic cold.
Continued Steady Cold – January (mean temperature: 6 F) and the first week and a half of February (mean temperature for the month: 13 F) continued in the steady cold pattern locked in since late November. Thawing afternoon temperatures were reached just twice over the first 41 days, roughly half the mornings subzero. Just a few days, however, had appreciable winds and there were no storms of any note. Such weather would be the promotional ideal a generation or so from now, as the first Minnesota boosters and publicists sought to sell its alleged healthy benefits to prospective settlers and visitors suffering from pulmonary ailments. The morning of the 3rd was -22 F, the 10th -18 F, and the 24th a frigid -32 F, the latter the lowest reading at the Post for another 17 years. On 11 February, the first extended thaw in two and a half months finally set in, this a day of “hail and rain alternately with thunder”. The next week had mostly thawing afternoons, some as mild as the mid-40’s, but Arctic cold then closed in again, each of the last seven mornings subzero.
Backward Spring – Spring ’21 was much more backward than a year ago, the rivers opening two weeks later, April and May both significantly cooler. Blustery weather featured March (mean temperature: 29 F), roughly half the days “windy” or with “high winds”. Afternoon temperatures displayed only a slight warming trend from beginning to end, alternating between the 40’s and 50’s for several day stretches back to subfreezing levels for several others. Conditions deteriorated over the first half of April (mean temperature for the month: 40 F), snow and high winds prevailing on the 8th, the 9th and 10th each failing to reach freezing. A snowstorm accompanied by strong winds left 4 inches on the 14th. This last system made the 1820-21 snow “season” six months and three days long, that much time having elapsed since last October’s great storm. The ice didn’t leave the Mississippi until the 18th, and the first really warm day didn’t come until the 27th, the mercury reaching 78 F at 2PM. May (mean temperature: 55 F) was mostly cool and clear with just a single rainy period, a three-day spell over the 23rd to 25th with “rain”, “rain”, and “rainy” entered in the “remarks” column of the diary. A brief warm spell over the second week brought 79 F on the 8th and 83 F on the 9th, but most of the month’s other afternoons were confined to the 60’s, this to be the coolest May for another fifteen years and the coldest April-May tandem for another twenty-eight.
Hot June, Cool July, Hot August – Summer 1821, several degrees warmer than last year, provided a fair but unusually distributed sample of the kind of sustained heat possible in this little-known area. June and August were both exceptionally warm but July was cool, an unusual month-to-month thermal “seesaw”, given the time of year; such a pattern has not been repeated to such a degree during Summer in these parts since. June (mean temperature: 73 F), brought unseasonably high temperatures almost from the first day, mid-to-upper-80’s recorded nearly every afternoon of the first week. Even warmer weather followed, the 11th hitting 95 F at 2PM, 98 F also noted (presumably the afternoon maximum) by Surgeon Purcell in a special remarks column entry. This 3 F spread between the 2PM temperature and the afternoon maximum is a typical one. Minneapolis-St. Paul afternoon absolute maxima on given summer days typically average about 2 degrees higher than 2PM readings, 1 degree warmer than those at 3PM. Displaying its natural inclination as the wettest calendar month climatologically in this region, fourteen days had rain, eight of these over the first twelve. A generation from now, logging and steamboat interests would rely expectantly on these early June rains together with those of the preceding days of late May to generate the “June-rise” of the rivers. Summer ’21 saw the first attempts at large-scale agriculture in the Fort vicinity. In addition to their continued construction activities, Colonel Snelling had his men plant acres of wheat, oats, and corn “procured from the Sioux” [Jones, 1962]. The results were mixed. Wheat and oats evidently did well, but the corn crop was “virtually destroyed by blackbirds” [Jones, 1962]. Temperatures over the first three weeks of July (monthly mean temperature: 71 F) retreated to cool and pleasant, afternoons mostly in the 70’s. But over the last eight days, a steady, protracted, hot and dry spell set in. From 24 July through 13 August, 88 F to 92 F afternoon temperatures were reached 15 out of the 21 days, with just a single thunderstorm occurring over the interval. Cooler, wetter, and considerably cloudier weather made up August’s remaining days, three afternoons over the last week confined to the 60’s, four days with rain. Still, monthly mean temperature (75 F) finished as the highest August figure locally for another 60 years.
Bright October, Cold December – This year’s fall to early winter transition was much smoother than 1820’s with no October snowstorms or November cold waves. Unseasonably early arctic cold was felt again, but its onset was delayed a couple of weeks into early December. Relatively mild weather made up September’s first half (mean temperature for the month: 60 F), afternoons frequently in the mid-to-upper 70’s, several thunderstorms occurring. But following more rain on the 19th accompanied by falling temperatures, the season’s first frost occurred two mornings later, followed by a “heavy” visitation on the 25th. October (mean temperature: 49 F), sunny and dry, had 21 “clear” days and just a single rainy spell covering two days. Cold weather was felt early, six consecutive afternoons beginning with the 6th confined to the 40’s, the mercury dipping to 30 F one morning. But on the 14th an extended spell of what must have been splendid Indian Summer weather set in, lasting two weeks. Afternoon temperatures well into the 60’s, sometimes the low 70’s, prevailed, accompanied by clear skies and winds predominating from the south quarter. Notes from the 15th report that “medical personnel commenced moving into the new Hospital at Fort St. Anthony”, weather conditions certainly no hindrance. Signs of impending winter appeared on Halloween, though, with snow and rain mixed and temperatures confined to the mid-30’s. November (mean temperature: 30 F) had more grey and dreary weather than last year, but without any arctic intrusions – no morning readings cooler than the teens. Afternoons after the first week were still chilly, confined to the 20’s and 30’s, with ice seen running down the Mississippi on the 10th, and the first blanket of snow laid down on the 16th. On the 26th, the St. Peter’s River was “sufficiently frozen above the mouth to crop”. December, equally cold as last year in the mean (10 F), started with a heavy, wet snowstorm (“about 8 inches”) on the 2nd. Temperatures through the end of the first week didn’t fall off immediately in its wake, the teens still noted for the mornings and the 20’s to low 30’s for the afternoons. Early of the second week, however, arctic weather set it, eighteen straight mornings from the 9th to 26th, inclusive, noting single figure or subzero readings. The month’s lowest temperature, -22 F, came on the 23rd. The Mississippi closed on the 10th, 15 days later than last year. On the 15th, Surgeon Edward Purcell wrote: “In comparison of this with last winter I find the present much milder thus far.”