ANNUAL CLIMATOLOGICAL SUMMARY
FT. SNELLING MN
The January-June portion of the 1855 Ft. Snelling climatological record consists of: four daily fixed time readings taken from the station's "detached" thermometer; daily precipitation values; four daily fixed time sky cover observations; four daily fixed time observations of wind "force" and wind direction; four daily barometric readings; and four daily readings from the station's "attached" thermometer (i.e. from an indoor thermometer used to adjust barometric readings for the effects of temperature on the station's mercury barometer) . January-June 1855 temperature, sky cover, wind direction/force and barometric observations were taken at or about local sunrise, at or about 0900 hours, at or about 1500 hours and at or about 2100 hours local solar time. Beginning 1 July 1855, however, observation schedules for all stations within the Surgeon General's reporting network were changed to include; a) outdoor temperature and hygrometric readings taken daily at 0700, 1400 and 2100 hours; wind direction and wind force readings taken daily at 0700, 1400 and 2100 hours; and c) descriptive sky cover observations (expressed, as before 1843, only as "cloudy" or "fair") taken daily at 0700, 1400 and 2100 hours. Similarly, barometric readings were taken at 0700, 1400 and 2100 hours, beginning 1 July (but apparently discontinued altogether on 31 October).
So far as can be determined, Ft. Snelling precipitation observation schedules and techniques were not significantly affected by the 1855 "reorganization" of the Surgeon General's meteorological network. Consequently, it is probable that all 1855 precipitation observations were taken at either 2100 hours or in the early morning (probably at sunrise during the first six months of the year and at 0700 hours during the last six months of the year). As in prior years, some precipitation values (particularly those which might have been obtained from early morning readings) may have been "shifted" from the date on which the observation was actually made to the day immediately preceding.
So far as can be determined, 1855 Ft. Snelling temperature readings were taken from an instrument manufactured by George Tagliabue, New York City and precipitation observations were taken from a DeWitt rain gauge (which was probably mounted on a pole or post on the fort's parade ground) . With the notable exception of January-June 1855 readings taken at 0900 hours, fixed time temperature readings taken by Ft. Snelling observers during 1855 appear to be consistent with normal diurnal patterns (indicating, in turn, that the station thermometer was, for the most part, located/sheltered as necessary to protect it from exposure to direct sunlight).
All 1855 wind force values are expressed in terms of a numeric wind force indicator selected by fort observers after visually noting the effect of wind on flags, trees, signs and other easily movable objects . As in prior years, 1855 monthly force of wind records are often incomplete: several air movement records include wind direction entries UNACCOMPANIED by corresponding wind speed indicators. Extant records give no explanation for these lapses: perhaps the missing entries indicate a force of wind value of more than zero but less than one or, alternatively, that fort personnel, for whatever reason, were unwilling or unable to expend the time and effort required to take consistent wind speed observations. Also, as noted previously, quantitative "clearness of sky" measurements were dropped from the Fort record on 1 July 1855, being replaced with general, daily descriptive entries which, so far as can be determined, indicated either that the sky was more than 50 percent obscured by clouds (designated as "cloudy") or less than 50 percent obscured (designated as "fair").
Like corresponding records from the years immediately preceding, the 1855 Ft. Snelling record appears to significantly understate the number of days with precipitation and/or measurable precipitation. This suggests that -- following the example of their predecessors -- Fort observers did not routinely/consistently measure and/or record small precipitation events, sometimes either ignoring less significant deposits of rain or snow (or. alternatively, using terms such as "inappreciable", "unmeasurable" or "slight" to denote small, but perhaps otherwise measurable, amounts of precipitation). This tendency is particularly evident in records for the winter months of year: St. Paul newspaper accounts -- together with contextual evidence from the 1855 record itself -- suggest, in fact, that Fort observers, for whatever reason, sometimes failed to measure or record significant portions of the precipitation which fell during the winter months (and, to a lesser extent, probably the summer months as well).
Although the 1855 Fort Snelling record includes daily liquid/melted precipitation values and a record of the TYPE of precipitation observed, it contains NO QUANTITATIVE snowfall values (whether of fresh snowfall or accumulated snow cover). Therefore, unless otherwise noted, snowfall values contained in the foregoing compilation are estimates inferred from newspaper accounts of 1855 snowfall events and/or obtained by applying the National Weather Service meltwater-snowfall conversion matrix to the meltwater values recorded by Ft. Snelling observers on 1855 "snow days".
As noted, analysis of the 1855 temperature record suggests that mid-morning readings taken during the first half of the year (like corresponding readings for several years prior) may have been compromised by improper instrument exposure and/or erratic observational schedules. Specifically, fixed time temperature readings taken during this period suggest an inordinate "compression" of daily readings taken at 0900 and 1500 hours. This suggests, of course, that the station thermometer may have been exposed to the direct rays of the mid-morning sun and/or that observations were sometimes taken at times significantly different than the times indicated in the official record .
The foregoing 1855 climatological record includes both unadjusted (UNADJ) and adjusted (ADJ) mean temperature values. Unadjusted values are the simple average of fixed time readings taken at sunrise/0900/1500/2100 (January-June 1855) and the weighted average of fixed time readings taken at 0700/1400/2100 (July-December 1855). 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 which would have been recorded had the Ft. Snelling station been equipped with self-registering thermometers read and re-set at midnight. The foregoing 1855 record also includes both the monthly and annual extremes (e.g. highest daily minimum) estimated by Fisk and the monthly extremes actually recorded by fort observers, All 1855 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.
All foregoing monthly mean cloudiness (January-June only) and force of wind values are the simple average of the station's fixed time sky cover and air movement observations. The foregoing prevailing wind values are based on fixed time wind direction observations: prevailing/predominate winds are those most frequently observed/recorded during any given month.
The amount of precipitation officially recorded by fort observers during March, April, June, July, August, October, November and December 1855 may significantly understate the amount of moisture which actually fell during these months: the records involved include several descriptive entries (e.g. showers) unaccompanied by any quantitative precipitation value.
In addition to the Ft. Snelling record, the 1855 east central Minnesota climatological record includes records kept by several St. Paul pharmacists. These records have survived in fragmentary form and only to the extent published in pioneer era St. Paul newspapers.
Wet, snowy January with brief cold wave late in the month. Abnormal warmth on 2 January: readings of 46 F, 54 F and 56 F at sunrise, 1500 and 2100, respectively. Reading of 50 F at Ft. Ripley at 2100 hours on the same date. St. Paul newspaper accounts indicate that the "streets were liquidated with dirty water and the weather was so mild and unseasonable that...some complained of the heat...there has been little snow this winter and old settlers state that the weather for mildness has seldom been equalled...". Cold, dry February: sunrise readings of -23 F on 24, 25 February. Cold, windy March: force five and force six winds recorded on many days during the month. Severe blizzard, 12-13 March. Sunrise readings of -16 F on 20, 21 March. Afternoon reading of 14 F on 27 March. Warm, very dry April. Afternoon readings of 86 F on 17 April, 88 F on 28 April. Prairie fires noted on 4, 6 April: smoky conditions on 28 April. Dusty conditions noted on several days during the month ("...dust was flying in the streets yesterday...a more disagreeable day we have near experienced..":St. Paul Pioneer, 23 April). Warm, dry May; Reading of 90 F at 1500 on 21 May. "Clouds of dust" noted in the streets of St. Paul (St. Paul Pioneer, 16 May). Low river levels and fears of impeded navigation noted at various times during May. Cool early June: reading of 54 F at 1500 on 1 June; 40 F at sunrise on 2, 4 June. Warm late June: readings of 95 F, 94 F and 95 F at 1500 on 26, 27, 28 June, respectively. St. Paul newspaper [13 June] noted that the "..river has not been so low during the month of June as it is now...". Damaging thunderstorm at Hastings during the night of 25-26 June. Warm sunny (twenty two "fair" days) July. Readings of 76 F, 79 F, 78 F and 82 F at 0700 on 15, 16, 17, 18 July, respectively. Reading of 96 F at 1400 on 18 July followed by a reading of 66 F at 1400 on 19 July. St. Paul pharmacist W. H. Morton W. H. Morton recorded 100 F at 1200 hours on 18 July. Only 1.32 inches of rain recorded at Ft. Snelling during July: St. Paul newspaper accounts indicate that several heavy rains occurred during the month (suggesting that the Ft. Snelling record is erroneous/incomplete). Rising river levels noted during month ("...we are blessed with rain...these days...plenty of it fell on Sunday night and Monday morning and a consequence is a rise in the rivers...": St. Paul Pioneer, 17 July 1855). Cool, cloudy August with heavy rains, 1-3 August (3.4 inches recorded at Ft. Snelling). Afternoon readings in the 60's F with cool, autumnal weather noted on many days during the month. Severe thunderstorms on 2, 3 August: damaging lightning strikes in St. Paul on 1 August. Warm, wet, cloudy September. Reading of 90 F at Morton's site at 1600 on 10 September. "Heavy and steady" rain on 22-23 September: 2.2 inches recorded at Ft. Snelling. Rain damage noted in St. Paul in late September: Mississippi river said to have risen more than five feet. Dry, sunny October. "We are now enjoying a beautiful Indian summer...the river is sufficiently high to allow good sized boats to reach the levee with little difficulty... (St. Paul Pioneer, 11 October). Reading of 80 F at Morton's site at 1200 on 18 October: 79 F at 1400 at Ft. Snelling on the same date. Reading of 68 F at Morton's station at 1200 on 31 October. Warm, wet November. Heavy rain on 10-11 November with thunderstorm on 11 November. Moderate snow cover with good sleighing reported during the closing days of November. Warm early December followed by extreme cold after mid-month. Readings of -33 F, -26 F, -25 F and -26 F at Ft. Snelling on 24, 25, 26, 28 December, respectively. Reading of -38 F at Morton's site at 0600 on 24 December; -36 F at St. Paul's Day and Jenks Pharmacy at 0600 on the same date. Heavy snow during December.