Minnesota (Fort Snelling) Weather for the year 1826
A Great Spring Flood –
The year 1826 provided the outstanding weather-related event of the pre-Territorial era: the great flood of late April. Heavy late March/early April snows followed by a long spell of unseasonably cold temperatures set the stage for the most severe flooding here for another generation. Annual mean temperature (44 F) was down 3 F from a year ago, although unseasonably early, prolonged warmth occurred in May and early June. The months October-December were also the mildest collectively in eight years’ history thus far. A record late closing of the Mississippi occurred as a consequence.
Variable Winter Temperatures, Increasing Snows – January (mean temperature: 9 F) and February (mean temperature: 14 F) provided an alternating mix of thaws and arctic spells to go with thirteen snow-days. The latter was the most recorded yet for these two months, a preview of things to come in March and April. Following a minus 12 reading on the morning of 4 January, temperatures climbed to the 30’s and low 40’s on six out of seven afternoons starting with the 7th. Another relatively mild January seemed to be shaping up, but over the 22nd-23rd, a sharp cold wave introduced a bitter arctic spell, five of the last eight mornings of January between -20 F to -23 F, the 30th only minus 13 at 2PM. Tempering the bitter cold’s sting, however, was arrival on the 26th of the first mail in five months, an event causing “great joy in the fort” [Williams, 1881]. Arctic weather carried over into February a few days with -18 F felt on the 3rd, but less than 36 hours later on the 4th the mercury soared to 49 F, rain falling during the day. The remainder of the month displayed short, alternating cold and warm spells. Morning temperatures sank to -20 F on the 14th and 15th, but 50 F was recorded on the afternoon of the 24th. Subzero mornings followed on each of the last three days. Special diary notes at the end of March recognized a mini-heat-island effect on temperature caused by the Fort enclosure and its many fires. As Surgeon B. F. Harney wrote: “A thermometer located 2 miles from this Post has on several occasions indicated greater cold by 10 or 11 degrees than is shown in the diary for the [1st] quarter. The thermometers were compared & found to agree. This difference is – no doubt – a consequence of the protection afforded by the buildings of the Fort and the number of fires almost constantly burning — 60 fires.”
Heavy Snows, Backward April, the Great Flood – March (mean temperature: 29 F) gave signs over the first two weeks that another early breakup might be imminent. Most afternoons reached at least the 40’s, some to the low 50’s, but a sudden turn around the equinox changed this outlook drastically, insuring 1826 a place in the early Minnesota history texts. On the 19th-20th, a massive snowstorm: “one and a half feet of snow drifted into heaps of six to fifteen feet” [Williams, 1881] suddenly struck. Fort Snelling evidently weathered the storm without any loss of life, but to the southwest, the deep accumulations proved deadly to some thirty Sisseton and Sioux Indian lodges in transit across the prairies. Trapped and unable to find food, many starved until rescue came from a group of Canadian fur trappers [Hansen, 1958]. With a high flood potential now at hand, the weather aggravated matters further by turning backward in early April (mean temperature for the month: 37 F). First, an additional eight-inch snowstorm, accompanied by thunder and lightning, buried the Post on the 5th. Then, an unseasonably late outbreak of arctic air dropped the mercury to 4 F on the 10th. Cold weather lingered for another week, delaying further the breakup of the rivers, and when the ice finally started to move on the 21st, the results were devastating. Near the Fort, all the buildings in the lowlands were carried away, including those of Jacques Faribault, the same unfortunate victimized by the high waters of June 1822. Downstream near the present-day site of South St. Paul, Chief Little Crow’s village was also swept away, the Sioux being forced to ultimately relocate three miles upstream [Minnesota Pioneer, 1853]. In the days following, low-lying Fort Crawford several hundred miles downstream was inundated, soldiers and settlers alike being “driven to the hills” [Jones, 1966]. Back at Fort Snelling, the river at the landing crested 20 feet above low water on the 24th, remaining at this level for several days. The ’26 flood set a high water benchmark that would stand for another quarter century, notable, but lesser, high water episodes not to be experienced again here locally until well into the 1840’s.
Great May Temperature Reversal, Warm Early Summer – Weather conditions after the first week of May underwent a sudden and dramatic shift to a long spell of unseasonable heat. Afternoon temperatures no higher than the low 50’s were recorded on several days early on, but starting with the 11th, an abrupt turnabout to mid-summer-like warmth set in, thirteen of the last twenty-one days reaching the 80’s, several around 90 F. Southerly winds predominated on all but two. May (mean temperature: 65 F) finished 28 F warmer than April, one of the greatest such warm reversals in the record down to the present. Precipitation during the month was ample (12 rain-days); nonetheless, diary notes reported St. Peter’s river “fallen 6 1/2 feet” on the 11th and the Mississippi down 6 feet on the 16th. This year’s navigation season would bring four steamboat arrivals to the Post, greater by one than the all the previous seasons combined. Visitors this month were the “Lawrence”, docking on the 2nd, the “Eclipse”, landing on the 7th, and the “Scioto”, arriving on the 27th. Premature heat extended through the first week of June (mean temperature for the month: 71 F), 92 F observed on the 2nd, the year’s warmest, and 88 F recorded on the 7th. But cooler more seasonable weather prevailed over the balance, most afternoons in the 70’s. Three successive afternoons during the third week reached the 86 F to 88 F range. Altogether, eleven days during June recorded rains. July (mean temperature: 73 F) was sunny and less rain-frequent with 21 clear days and seven with rain. The 3rd to 11th was the summer’s warmest period, all but one afternoon in the 86 F to 90 F range, but thunderstorms on the night of the 11th terminated the spell, no 2PM readings higher than 84 F noted again through the close. Diary entries on the 4th, the fiftieth anniversary of the Declaration of Independence, indicated “Clear” skies, westerly winds, and a 2PM temperature of 86 F. August (mean temperature: 69 F) was pleasant with only two afternoons as warm as 85 F and seven rain-days. The 12th-18th was the warmest period, afternoon readings ranging from 80 F to 87 F, but cooler weather made up the balance, most afternoons in the low-to-mid-70’s.
Cool September, But Mild October /November and a Delayed Rivers’ Closing – Except for a cool and damp September, the remaining months of 1826 showed the most gradual descent to winter in eight years’ experience (including 1819). September, overcast, rainy, and chilly, had 18 “cloudy” days, 14 with rain, and only one afternoon warmer than 70 F after the first week. Monthly mean temperature (55 F) would not be surpassed for coolness until 1841. Resuming the trend for early frosts, the season’s first visitation came on the 11th, only a few subsequent morning readings warmer than the mid-40’s. Some notable falls of rain came over the last week-and-a-half: a “rain all night” entry shown for the 23rd, a “rain during the day and night” appearing for the 24th, and “a rain all day” indicated for the 27th. October in marked contrast, was sunny, dry, and mild. Twenty-four days were designated “clear”, just four had rain, and monthly mean temperature (49 F) tied 1821 for warmest in eight years. Summery weather set in during the first week, 82 F recorded on the 5th accompanied by “fresh” southerly winds, most of the other afternoons over the first two weeks at least approaching 70 F. The first reported frost didn’t come until the 18th, a few other mornings before the close dropping into the mid-20’s. Most daytime readings were in the upper 40’s to upper 50’s. November (mean temperature: 35 F) was the mildest in eight years. Most afternoons were in the 40’s, only a few reaching the 50’s, but no arctic incursions were felt, just two mornings as low as the upper teens noted. The month opened with nine consecutive “cloudy” days, including a two-inch snowfall and two rain-days, but eleven of the next fourteen were “clear”, the mildest afternoons of the month, 58 F and 60 F, coming on the 14th and 15th, respectively. The last week saw some wintery signs, afternoon readings in the low to mid-30’s, snow falling on several days, and ice seen running in the Mississippi. Unseasonably mild weather returned again over the first half of December (mean temperature for the month: 19 F), afternoon temperatures reaching the 40’s on several days, including 48 F on the 12th. The closing of the Mississippi was delayed until the 20th, breaking 1824’s late date mark by eight days. Arctic air finally closed in on the 22nd, dropping the mercury just below zero for the first time. Progressively colder weather followed with -18 F read on the 27th and -19 F on New Year’s Eve morning.