ANNUAL CLIMATOLOGICAL SUMMARY
FT. SNELLING MN
The 1826 Ft. Snelling climatological record consists of fixed time temperature readings taken daily at or about 0700, 1400 and 2100 hours local solar time; single daily entries indicating the prevailing direction of the wind and the general condition of the sky; intermittent records of snowfall and/or snow cover; episodic records of phenological, hydrological, astronomical and/or other natural events (windstorms, prairie fires, etc.); descriptive entries indicating the general duration (and, in some instances, the intensity) of precipitation; precipitation type ; and special atmospheric phenomena (fog, smoke, etc.). So far as can be determined, all 1826 observations were taken within the Ft. Snelling enclosure (on the bluffs overlooking the confluence of the Mississippi and Minnesota [then the St. Peters] rivers) .
Analysis of the relationship between 0700, 1400 and 2100 readings indicates that the station thermometer was probably exposed to direct morning and/or afternoon sunlight during the warm months of 1826. Specifically, 1826 summer temperature records (late May through early August) include numerous 0700 readings exceeding or equaling 2100 readings (thereby reversing or nearly reversing normal summertime diurnal patterns). Such patterns obviously suggest that 1826's warm season average temperatures were elevated by direct exposure to early morning sunlight: the original record indicates, for example, that June, July and August 1826 temperatures averaged about 71 F, 73 F and 69 F, respectively (as adjusted by Fisk, cited below), values which, when further adjusted for the probable effects of sun contamination , are reduced to 69 F, 71 F and 67 F, respectively.
The foregoing 1826 temperature record includes both unadjusted (UNADJ) and adjusted (ADJ) mean temperatures. Unadjusted values are the averages of fixed time readings taken daily at 0700, 1400 and 2100 hours . Adjusted averages are from Charles J. Fisk's 1984 "Reconstruction of Daily 1820-1872 Minneapolis-St. Paul Temperature Observations". These values were obtained from statistically derived estimates of the daily maxima and minima that would have been recorded had the Ft. Snelling station been equipped with self-registering thermometers read and re-set at midnight . The foregoing 1826 record also includes both the monthly and annual extreme temperatures (highest daily minimum, lowest minimum, etc.) estimated by Fisk and the monthly extremes actually recorded/observed (OBSRV) by fort observers. All 1826 temperature distributions (e.g. days 90 F or higher, 32 F or lower, etc.) are based on Fisk's estimates of daily maxima and minima.
Although no quantitative precipitation records were kept at Ft. Snelling during 1826, extant records do, as noted, contain entries indicating precipitation type and, in some instances precipitation intensity (e.g. light snow, heavy rain, etc.). These records are the basis of the foregoing 1826 precipitation frequency record (e.g. number of days with snow, etc.) . Prevailing wind values, similarly, are based on entries indicating the predominate direction of the wind on each day of the month. Prevailing monthly winds indicate the direction most frequently observed/recorded during any given month.
Warm early January: readings of 37 F, 35 F and 35 F, respectively, at 0700 hours on 8, 9, 13 January. Very cold late January: three consecutive days with all fixed time readings below zero, 23-25 January. Reading of -13 F at 1400 hours on 30 January. Thirteen cloudy days during January. Warm early February: reading of 49 F at 1400 hours on 4 February. Cold mid-February and again late February. Probable heavy snowfall over much of what is now Minnesota during January and February. Snowy, cloudy (fifteen cloudy days recorded) March. Massive snowstorm, 19-20 March: snowfalls of eighteen inches probable in what is now southwestern Minnesota. Drifts reported six to fifteen feet and depth: much loss of life among Sisseton and Sioux Indians. Snow noted by Ft. Snelling observers on 19 March but no amount indicated. Southeast winds prevailing on 18 March, shifting to the north on 19 March. March was probably one of the snowiest Marches in the 180 year Twin Cities area record (with total snowfall perhaps approaching forty inches). Wet, cold and cloudy (sixteen cloudy days) April. Early April cold wave: readings of 4 F and 24 F, respectively, at 0700 and 1400 hours on 10 April. Snowfall of about eight inches noted on 5 April. Severe and extensive flooding caused by spring snowmelt: Indian village near what is now So. St. Paul swept away, Ft. Crawford (several hundred miles downstream) temporarily evacuated because of Mississippi river flooding. Ft. Snelling landing on the Minnesota [St. Peter's] river said to have inundated by a crest twenty feet above the low water mark (24 April). Rainy, warm May. Cool early May with snow noted on 4 May. Rapid warm-up following: temperatures in the 80's F, 11-15 May. Readings of 78 F at 0700 on 14 May, 80 F at 0700 on 26 May . Southeasterly or southwesterly winds prevailing on 25 days during May. Sixteen cloudy days during June. "Very windy" on 4 June. Warm early June: 92 F recorded at 1400 on 2 June. Warm early July: afternoon temperatures in the high 80's or low 90's F, 2-11 July. Many 0700 hour readings in the 80's F during the same period. Twenty one clear days during July. Cool and relatively rainy August: rain "all night" on 24-25 August. Cool, rainy September. Several days with prolonged rainfall. Light frost on 11 September. Eighteen cloudy days during September, most of them recorded during the first half of the month. Sunny (twenty four clear days), dry October. Many days with westerly or southwesterly winds prevailing. Mild, cloudy (sixteen cloudy days) November. Two inches of snow on 3 November. High winds and snow on 16, 29 November. Reading of 60 F at 1400 hours on 15 November. Warm early December: 48 F at 1400 on 12 December. Southwesterly or westerly winds prevailing on twenty four days during December. Cold and snowy late December. High winds on 26, 29 December. Reading of -19 F at 0700 on 31 December.