ANNUAL CLIMATOLOGICAL SUMMARY
FT. SNELLING MN
The 1828 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 1828 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 1828. Specifically, 1828 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 1828's warm season average temperatures were elevated by direct exposure to early morning sunlight: the original record indicates, for example, that May and July 1828 temperatures averaged about 59 F and 74 F, respectively (as adjusted by Fisk, cited below), values which, when further adjusted for the probable effects of sun contamination , are reduced to about 58 F and 73 F, respectively.
The foregoing 1828 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 1828 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 1828 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 1828, 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 1828 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 clear days recorded) and cold January. Temperatures near -30 F on 20-21 January. Two inch snowfall noted on 8 January. Snow accompanied by "high winds" on 27-28 January. Snowy, cloudy (sixteen cloudy days) February. Sixteen hour snowstorm, 20-21 February. Twenty four hour snowfall on 25-26 February. Mid-February thaw: temperatures of 49 F and 50 F at 1400 hours on 15, 16 February, respectively. Late February-early March cold wave: -22 F at 0700 on 29 February; -18 F at 0700 on 3 March; and -15 F at 0700 on 4 March. Generally mild mid-March to late March. Three inch snowfall on 25 March followed by rain, thunder and lightning on 26 March. Heavy rain on 27 March followed by snow on 28 March. Twenty clear days recorded during March. Cold early April: readings of 30 F, 32 F and 30 F, respectively, at 1400 on 3, 4, 5 April. Snowy early April Mild, dry mid-April: temperatures near 80 F on 21 April. Reading of 61 F at 0700 on 21 April . Wet late April - early May. Snow on 25 April. Heavy rains on 1, 4, 10, 15 May. Snow from about 1800 hours on 11 May until about 0900 on 12 May: no amount indicated, but significant accumulation probable. Rain with "high winds" on 28, 31 May. Rainy, warm June. Very sunny (twenty nine clear days), dry and warm July. Afternoon temperatures near or above 90 F, 15-25 July. Many early morning readings in the 80's F, 17-25 July. Only two July days with rain noted. Very dry (only one day with rain) and sunny (twenty six clear days) August. Persistent (but no extreme) warmth during August. Dry (rain noted on two days) and sunny (twenty two clear days) September. Prevailing winds from the west and southwest on seventeen days during September. No frost noted during September. Sunny (twenty seven clear days) and dry (rain noted on only one day) October. Prevailing winds from the west or southwest on eighteen days during October. Warm weather prevailed during much of October; reading of 60 F at 0700 on 23 October. Warm but cloudy (twenty three cloudy days) November. Precipitation frequent during November. Warm, sunny (eighteen clear days) and dry December. Snow on only two days during December. Several days with afternoon temperatures near 50 F during the last week of December. Sixteen days with prevailing winds from the west or southwest. Reading of 38 F at 0700 on 16 December.