ANNUAL CLIMATOLOGICAL SUMMARY
FT. SNELLING MN
The 1827 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 1827 observations were taken within the Ft. Snelling enclosure(on the bluffs overlooking the confluence of the Mississippi and Minnesota 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 1827. Specifically, 1827 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 1827's warm season average temperatures were elevated by direct exposure to early morning sunlight: the original record indicates, for example, that May, June and July 1827 temperatures averaged about 61 F, 71 F and 73 F, respectively (as adjusted by Fisk, cited below), values which, when further adjusted for the probable effects of sun contamination , are reduced to about 60 F, 70 F and 72 F, respectively.
The foregoing 1827 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 by averaging statistically derived estimates of 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 1827 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 1827 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.
In an apparent effort to conceal the loss of whatever original records may have been kept during that month, fort surgeons "faked" the October 1827 record with values transcribed from the October 1826 record. The resulting gap in the 1827 temperature record was filled by Fisk (op. cit.) with regression derived values based on October 1827 temperature records kept at Ft. Howard (Green Bay) WI.
Although no quantitative precipitation records were kept at Ft. Snelling during 1827, 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 1827 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.
Mid-January cold wave followed by late January warmth. Fourteen cloudy days recorded. Southwesterly of westerly winds prevailed on twenty days during January. Very mild, sunny (twenty one clear days) February. Afternoon readings in the mid to high 40's F on many days. Snowstorm with high winds on 27 February. Prevailing southwesterly or westerly winds on twenty three days during February. Windy, snowy March. Snow storms with high winds on 17, 27 March. Reading of 56 F at 1400 on 5 March. Cloudy (seventeen cloudy days) and windy April. Prevailing winds from the west or southwest on twenty one days during April. Sunny (twenty two clear days) and windy May. Reading of 86 F at 1400 on 12 May. Cloudy (sixteen cloudy days), warm June. Reading of 85 F at 0700 on 28 June . Reading of 56 F at 1400 on 21 June. Prevailing winds from the southern quadrant on twenty one days during June. Warm July. "A gale from the southeast accompanied by torrents of rain" on 12 July. Probable maxima near 100 F on several days at the end of July. Cool, cloudy early August followed by warm, sunny late August. Heavy mid-August rains. Summery conditions during the first week of September: 90 F recorded at 1400 on 5 September. Northeasterly "gale" on 11 September followed by rain "all day" on 12 September. Rain "all day and night" on 15-16 September. Very cold late September: frost on 23, 24, 25, 26, 37 and 30 September with probable overnight minima in the high 20's F on 27 September. Reading of 46 F at 1400 on 30 September. Dry, sunny October (so far as can be determined: as noted, original October 1827 record is missing). Sunny, warm early November: 62 F recorded at 1400 on 9 November. Cloudy, cold late November. Prevailing winds from the west or southwest on seventeen days during November. Cold, cloudy (eighteen cloudy days) December. Snow accompanied by "northeast gale" on 6 December (following rain and sleet on 5 December).