ANNUAL CLIMATOLOGICAL SUMMARY
FT. SNELLING MN
The 1830 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 1830 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 1830. Specifically, 1830 summer temperature records (late 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 1830's warm season average temperatures were elevated by direct exposure to early morning sunlight: the original record indicates, for example, that temperatures averaged about 67 F in June and about 80 F July 1830 (as adjusted by Fisk, cited below), values which, IF further adjusted for the probable effects of sun contamination , would be reduced to about 66 F and 79 F, respectively.
The foregoing 1830 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 1830 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 1830 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 1830, 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 1830 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.
Sunny (twenty five clear days) and dry (light snow on four days) January. Prevailing winds from the west or southwest on twenty two days during January. Very warm mid-January: reading of 47 F at 1400 on 14 January. Very warm and sunny (twenty one clear days recorded) February. Only one day with significant snowfall. Prevailing winds from the west or southwest on twenty one days during February. Cold early February followed by near record warmth at mid-month: readings of 54 F, 54 F and 57 F at 1400 hours on 9, 13, 14 February, respectively. Readings of 34 F at 0700 on 15, 16, 17 February and 40 F at 0700 on 19 February. Warm late March: readings of 54 F at 0700 on 20 March and 61 F at 1400 on 19 March. Mississippi river at a "very low" stage on 31 March. Prevailing winds from the west or southwest on twenty days during March. Wet, cloudy (eighteen cloudy days recorded) April. Warm April: readings of 62 F and 81 F at 0700 and 1400, respectively on 5 April; 60 F and 63 F at 0700 hours on 18 and 20 April, respectively . Reading of 84 F at 1400 hours on 28 April. Cool May with three inch snowfall on 4 May. Twenty clear days during May: prevailing winds from the west or southwest also on twenty days. Light frost on 20, 21 May. Reading of 32 F at 1400 hours on 4 May. Cool, sunny (twenty four clear days) June. Reading of 58 F at 1400 on 18 June. Prevailing winds from the west or southwest on nineteen days during June. Dry, record warm July: afternoon temperatures in the high 80's and low 90's F virtually every day during month. Twenty six clear days recorded: prevailing winds from the southern quadrant on nineteen days. Readings in the 80's F at 0700 each day, 5-8 July, 12-20 July and 23-26 July. Very dry (rain on only two days) August. Warm early August followed by cooler conditions during the latter portion of the month. Cloudy (fifteen cloudy days) September. Frost noted on 15 September. Cold rain with a reading of 49 F at 1400 hours on 11 September. Very warm October: readings of 80 F and 82 F, respectively at 1400 on 25, 26 October. Reading of 66 F at 0700 on 26 October. Prevailing winds from the west or southwest on sixteen days during October. Record warm and very cloudy (twenty four cloudy days noted) November. Prevailing winds from the west or southwest on eighteen days during November. Very little snow during November. Cold, very snowy December. Snow noted on fifteen days during month. Eighteen cloudy days during December. Warm early December: 45 F at 0700 hours and 53 F at 1400 hours on 1 December. Very cold mid-December: reading of -10 F at 1400 on 20 December and -26 F at 0700 on 21 December. Deep snow cover probable during much of December.