ANNUAL CLIMATOLOGICAL SUMMARY
FT. SNELLING MN
The 1857 Ft. Snelling climatological record consists of: a) temperature and hygrometric readings taken daily at 0700, 1400 and 2100 hours; b) 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. So far as can be determined, 1857 Ft. Snelling precipitation observations were taken either at 2100 hours or in the early morning (probably at or about 0700 hours, at the time of the first daily temperature observation). 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, 1857 Ft. Snelling temperature readings were taken from an instrument manufactured by George Tagliabue, New York City and precipitation observations were taken from a DeWitt conical rain gauge mounted on a pole or post on the fort's parade ground . Fixed time temperature readings taken by Ft. Snelling observers during 1857 appear to be consistent with normal diurnal patterns (indicating that the station thermometer was, for the most part, located/sheltered as necessary to protect it from exposure to direct sunlight). All 1857 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 noted, 1857 sky cover values are expressed descriptively as "cloudy" or "fair", terms 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 1857 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 1857 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 1857 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 1857 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 1857 "snow days".
The foregoing 1857 climatological record includes both unadjusted (UNADJ) and adjusted (ADJ) mean temperature values. Unadjusted values were calculated by taking a weighted average of the station's 0700/1400/2100 fixed time readings. 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 1857 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 1857 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 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.
In addition to the Ft. Snelling record, the 1857 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.
Snowy, sunny (twenty two "fair" days recorded) and record cold January. Readings of -25 F, -31 F, -26 F, -35 F, -24 F recorded at 0700 on 5, 15, 17, 18, 23 January, respectively. Readings of -29 F and -38 F at W. H. Morton's pharmacy in St. Paul at 0600 on 5, 15 January, respectively. Other early morning readings as low as -40 F on 18 January. Blizzards with heavy snowfall on 13 and 30-31 January. No temperature above 32 F recorded at Ft. Snelling during the entire month of January. Very cold early February: reading of -35 F at Ft. Snelling at 0700 hours on 10 February with early morning readings near -40 F reported at several St. Paul sites on the same date. Severe blizzard, 5-7 February: snowfall of ten to fourteen inches probable. Thawing conditions on many days in late February. Cold but relatively dry March; reading of -19 F at 0700 on 7 March. Snowy, windy and record cold April: readings of 3 F, 13 F. 11 F and 12 F at 0700 on 6,15, 16, 17 April, respectively. Readings of 6 F, 2 F and 10 F at Morton's site at 0600 on 15, 16, 17 April, respectively. Snowstorm on 12 April. Force seven winds on 10 April and force five and force six winds on many other days during the month. Prairie fires noted on 19 April. First boat through Lake Pepin arrived in St. Paul on 1 May, the latest date ever for the opening of navigation. Cold, windy May: readings of 37 F at 1400 and 26 F at 0700 on 9, 10 May, respectively. Prairie fires observed on 9 May. Cool, wet June: readings of 54 F and 52 F at 1400 on 16, 17 June, respectively. Violent thunderstorm with hail on 7 June. Severe thunderstorm with 2.5 inches of rain on 14-15 June. Extensive local flooding noted in St. Paul on those dates. Rivers at or near flood stage during June. Warm, very dry and sunny (twenty six "fair" days recorded) July: 100 F at Morton's St. Paul station at 1200 on 25 July, 91 F recorded at Ft. Snelling at 1400 on the same date. St. Paul newspapers complained of blowing dust in the streets on several days during July. Warm early August, cool late August. Violent thunderstorm during the night of 6-7 August: wind damage with large hailstones noted in St. Paul. Grasshopper infestation reported at Ft. Snelling in early August. Warm September. No frost observed during month. Heavy rains with rising river levels at mid-month. Very dry but relatively cloudy (seventeen "cloudy" days recorded) October. Only a trace (T) of precipitation recorded at Ft. Snelling during the entire month of October. Cold, record wet November. Rain and snowstorm on 7-8 November produced nearly three inches of moisture at Ft. Snelling (an amount which may be understated: observer noted that station "snow gauge" was blown down during the night, "measurement, therefore, of less than full quantity") . St. Paul Pioneer (10 November) indicated that "...a section of this country was visited...Saturday night by a steady and long continued snow storm which left the ground covered with about four inches of snow...there was a much larger quantity than that but it melted quite rapidly...". Cold wave late November: -11 F at 0700 at Ft. Snelling on 23 November, -14 F at Morton's St. Paul site at 0600 on the same date. Warm, wet, snowy December. Ft. Snelling record suggests very heavy snowfall during month: St. Paul newspaper accounts suggest, in contrast, that snowfall was relatively modest and that sleighing was poor during much of month. Five inch snow cover noted on 13 December: six inch snow cover at the end of the month . No subzero temperatures recorded during December. Afternoon readings in the mid to low 30's F on many days. Reading of 47 F at 1400 on 13 December.
For additional information relating to weather conditions during the winter months of 1857, see the Technical Notes section of this compilation.