Minnesota (Fort Snelling) Weather for the Year 1825
Exceptionally Mild Winter/Early Spring
Weather conditions at (now) Fort Snelling displayed a markedly different character during 1825 with mild to unseasonably warm temperatures virtually all year accompanied by ample, well-distributed precipitation, especially over May and June. The Mississippi opposite the Post had its earliest Spring breakup yet, and for the first time in six years’ history, no September frosts were noted. Annual mean temperature (47 F) was up 4 degrees F from a year ago, start of a long run of relative mild years in which nine of the coming ten including this one would be warmer than the first five. Much of 1825’s anomalous warmth, especially in the early months, was likely attributable to a moderate El Nino prevailing in the Equatorial Pacific.
Warmest Winter and Early Spring By Far – Winter and early Spring ’25 featured a steady mildness far exceeding what had been previously known at this time of year, mean temperature for December ’24-April ’25 (31 F) more than 10 F warmer than any previous such period. January (mean temperature: 14 F) provided virtually all the winter’s cold weather, and this only moderate in character. Lowest thermometer reading all month was “just” minus 14 F, highest such January figure until 1837. Most afternoons reached the 20’s, a few getting into the 30’s, and similar to December, there were no days of “fresh” or “high” winds. The only significant snow was a three-inch fall over the first week. After a few bitter days to start February, including a winter minimum -15 F on the 3rd, a remarkably mild, cloudy, and damp regime set in, lasting almost uninterruptedly through the end of March. Such a pattern would not repeat itself for another 53 years, during the memorable “Year Without a Winter” of 1877-78. Both the 1824-1825 and 1877-1878 winters coincided with El Nino/Southern Oscillation (ENSO) episodes [Quinn, 1978], periodic warmings of the far away Equatorial Pacific Ocean that have been linked to anomalous weather conditions in higher latitudes (e.g., heavy winter rainfall in Southern California or mild winters in the Upper Midwest. Other Quinn identified ENSO’s that encompass the 1820-1869 period of study include 1819-20, 1821-22, 1828-29, 1832-33, 1837-38, 1844-45, 1845-46, 1850-51, 1852-53, 1855-56, 1857-58, 1864-65, and 1868-69. All but one of February ’25’s remaining days surpassed at least 30 F, and each of the last ten reached the low 40’s to low 50’s. The night of the 19th-20th brought a six-inch fall of wet snow, but its stay on the ground was likely quite brief. Mean temperature for February (28 F) finished 10 F above average. March’s usual changeable and blustery character was totally absent this year, the steady succession of unseasonably mild days with temperatures in the 40’s and 50’s continuing. Monthly mean temperature (38 F) tied 1822 for warmest thus far in the record. Similar to February, eighteen days were “cloudy” or had southerly winds, and nearly all the nights were thawing. Nine days had rain, none snow. The Mississippi started its earliest observed breakup, on the 15th, becoming ice-free on the 23rd. Day-to-day sky conditions brightened considerably in April with the unusually forward warmth becoming even more pronounced. Monthly mean temperature for the month (55 F) still ranks as the third highest figure in local climatic history – no freezing temperatures were recorded at any of the 7AM observation times. Four rains fell during the first week, but during the second and third, daytime skies were almost exclusively sunny with afternoon readings occasionally reaching the mid-70’s to low 80’s. The last week brought the first major circulation shift in nearly three months, predominant winds changing to westerly/northwesterly with afternoon temperatures confined to the 50’s and 60’s.
Warm, Wet Growing Season – Warm, relatively “cloudy” weather with ample rains characterized the rest of the ’25 growing season (May-August), vegetation and gardens perhaps the most developed in six years. May (mean temperature: 60 F) displayed steady day-to-day temperatures with frequent showers, all but six of the afternoons in the 60’s and 70’s, fifteen days recording rain. Each day over the 3rd to 15th was “cloudy”, eight having precipitation, the last five days of the month reporting showers and thunderstorms as well. Taking advantage of some evidently high river stages, the “Rufus Putnam”, third steamboat in history to reach the Post, became the first to navigate the St. Peter’s River, plying as far upstream as the post of the Columbia Fur Company, “Land End” [Ludlum, 1968]. The “Putnam” had first reached the Post this season on 2 April [Williams, 1882]. Hundreds of miles to the Northwest at the British Selkirk settlement near present-day Winnipeg, the month of May might also have been a time of severe flooding, Williams  reporting an episode there sometime during the year. June (mean temperature: 69 F), brought 21 “cloudy” days and 10 with rain, all of the latter over the first 20 days. Prevailing winds were from the south quarter on all days but four, only one afternoon, however, reaching as warm as the upper 80’s, that being 87 F on the 7th. Notes of a falling Mississippi river appeared on the 19th, 23rd, and 27th. July was warm (mean temperature: 75 F), and “cloudy”, 23 days so designated. Rain fell on 12 days, well-scattered through the month. The summer’s hottest afternoon came on the 9th with 94 F at 2PM, but the season’s warmest spell prevailed for eight days over the 15th-22nd, each having afternoon temperatures in the mid-80’s to low 90’s. Just three days had prevailing winds from the north quarter. Generally more pleasant weather comprised August (mean temperature: 70 F) with almost no hot days. The mercury hit 89 F for month’s warmest on the 7th, a couple of additional days reaching the mid-80’s during the second week, but thereafter few afternoons climbed out of the 70’s. Seventeen “cloudy” days were recorded and nine had rain. September (mean temperature: 62 F) was the mildest thus far in six years with no frost, the first such non-occurrence for this month. Like May, a uniform day-to-day pattern of afternoon temperature levels was evident from register observations, all but three in the 60’s and 70’s, none in the 80’s. A few mornings during the last week dipped into the low 40’s, but they were accompanied by “cloudy” skies. In all there were 14 “cloudy” days and eight with rain.
October Cold Turn, Large November Temperature Swings– After eight successive months of generally above average warmth, October (mean temperature: 46 F) and November (mean temperature: 34 F) each displayed large contrasts in thermal anomalies. The former brought a late edition of summery weather over the first five days, each of the afternoons between 79 F and 82 F, accompanied by clear skies and light southwesterly winds. Windy, cloudy, and gradually descending temperatures followed, however. The 7th was only in the low 50’s with “fresh” northerlies, the 14th just 40 F at 2PM. The morning of the 17th brought the season’s first frost accompanied by “fresh” northwesterlies, and following a four-day rainy spell, the passage of a powerful cold front produced one of the bitterest October days ever recorded here locally – before or since. Temperatures on the 27th were confined to 20 F, 24 F, and 20 F at the standard observation times attended by “high” northwesterly winds. In typical autumnal fashion, though, a strong warming trend ensued, afternoon temperatures back in the 60’s by the first week of November for several days accompanied by unseasonably late thunderstorms. Temperatures on the 6th were a September-like 64 F, 69 F, and 65 F at the prescribed observation times, but after heavy rains and passage of a sharp cold front overnight, readings in the 20’s returned by the following morning. The next two weeks were mostly cold and blustery, afternoon temperatures typically in the 20’s, coupled with “fresh” or “high” northwesterly winds. Snow also fell on several days. Winter seemed to be taking another early start, but in another great thermal upswing, not unlike a year ago about this time, mild levels returned on the 22nd, 48 F noted at 2PM. Temperatures warmed a bit more, each of the next seven afternoons reaching the 50’s, and then, in a climax of sorts, the mercury soared to 69 F on the 29th, a highest ever so late in the season mark locally that has stood through the present day. A second cold wave then sent temperatures plummeting nearly 50 F over the next 24 hours. On balance, November’s mean temperature finished at 34 F, several degrees above average.
Steady Cold for December – Winter was firmly settled in with the start of December (mean temperature for the month: 13 F), “drifting snow” and afternoon temperatures in the low teens prevailing on the 1st. On the 6th, the Mississippi closed for the winter, temperatures remaining below freezing until the 14th when 40 F was reached, the month’s warmest. Only three others reached 32 F before the close. The month’s lowest temperature, a comparatively moderate -14 F, was registered on the 26th. Overall, the month was comparatively sunny, 24 “clear” days, three with snow, and one with snow & rain mixed. Up at the Selkirk settlement near present-day Winnipeg, Canada, events were considerably less benign, a severe storm around the 23rd reportedly driving the buffalo away, burying people in snowdrifts and causing mass starvations in the period following [Ludlum, 1968].