ANNUAL CLIMATOLOGICAL SUMMARY
FT. SNELLING MN
The 1832 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 1832 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 at least some portion of the late spring and summer months of 1832. Specifically, 1832 summer temperature records (May through early August) include numerous 0700 readings exceeding or equalling 2100 readings (thereby reversing or nearly reversing normal summertime diurnal patterns). Such patterns obviously suggest that 1832's warm season average temperatures were elevated by direct exposure to early morning sunlight: the original record indicates, for example, that temperatures averaged about 55 F in May and about 71 F June 1832 (as adjusted by Fisk, cited below), values which, IF further adjusted for the probable effects of sun contamination , would be reduced to about 54 F and 70 F, respectively.
The foregoing 1832 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 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 1832 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 1832 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 1832, 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 1832 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 mid-January: reading of 46 F at 1400 hours on 16 January. Readings of 37 F and 38 F at 0700 on 16, 17 January, respectively. Rain and snow on 17 January. Very cold late January: readings of -26 F at 2100 hours and 0700 hours, respectively, on 24, 26 January. Reading of -14 F at 1400 on 24 January. Minimum near or below -30 F probable in vicinity of fort on 26 January. Sixteen cloudy days during January. January snowfall was probably moderate with little or no snow cover likely during much of the month. Cold, cloudy (fourteen cloudy days) February. Moderate (perhaps even heavy) snowfall during early February. Record late season cold, 22-23 February: reading of -30 F at 0700 on 23 February. Warm March with temperatures near 60 F during the first week of the month. No snow recorded during March. Brief mid-March cold wave: readings of -2 F at 0700 on 16 March and 9 F at 1400 hours on 16 March. Warm late March: readings of 74 F at 1400 on 29 March and 58 F at 0700 on 30 March. No precipitation recorded, 11-29 March. Warm, dry April. Readings of 64 F and 68 F at 0700 hours on 24, 25 April, respectively . Cool, cloudy (twenty two cloudy days recorded) May. Cold at mid-month: probable snowfall and a reading of 42 F at 1400 on 14 May. Warm, cloudy (sixteen cloudy days) June. Hail on 29 June. Dry, warm and sunny (twenty "fair" days recorded) July. Only four days with rain during July. Cool and moderately wet early August. No rain noted, 13-26 August. Very cool conditions during the closing days of August: readings of 56 F at 1400 on 30 August and 42 F at 2100 on 31 August. Temperature of 34 F observed at 0400 hours on 31 August. Warm September. Frost noted on 22 September. Hail on 20 September. Warm, sunny (twenty three "fair" days) October. Rain and cloudy weather during early October followed by very dry and mild weather during much of the remainder of the month. Prevailing winds from the west or southwest on sixteen days during October. Cloudy (nineteen cloudy days) November. Brief cold period at mid-month: 15 F recorded at 1400 on 18 November. Very warm December with light to moderate amounts of snow. Twenty cloudy days during December. Readings of 49 F and 45 F at 1400 hours on 30, 31 December, respectively. Reading of 35 F at 0700 on 7 December.