ANNUAL CLIMATOLOGICAL SUMMARY
FT. SNELLING MN
The 1858 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, 1858 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, 1858 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 1858 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 1858 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, 1858 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 1858 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 1858 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 1858 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 1858 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 1858 "snow days".
The 1858 Ft. Snelling record ends on 30 April 1858, the result of a federal decision to de-commission the Ft. Snelling facility and to lease out the military reserve on which the fort was located . The May-December portion of the foregoing 1858 record is, accordingly, comprised of estimated values and/or values obtained from newspaper accounts of 1858 weather events (including the published portions of "thermometric" and other records kept by several St. Paul residents at their respective places of business).
The foregoing 1858 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 (January-April). 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 during the first four months of 1858 had the Ft. Snelling station been equipped with self-registering thermometers read and re-set at midnight. Adjusted temperature values for the period, May through December 1858, are regression derived estimates based on records kept by a Smithsonian observer at Dubuque, Iowa . The foregoing 18587 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 (January-April only). All 1858 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 Ft. Snelling fixed time sky cover and air movement observations (January-April). 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 (January-April).
In addition to the Ft. Snelling record, the foregoing record includes snowfall values recorded by St. Paul observer William Kelly (November and December 1858) and estimated/interpolated average temperature and precipitation values, May-December 1858. The latter set of values -- taken from a St. Paul climatological summary prepared by the U.S. Weather Bureau in 1931 -- may be from 1858 records kept in Minneapolis by C. L. Anderson, M.D. Unfortunately, however, the publication involved does not clearly indicate the source of these data: moreover, any 1858 records which may have been kept by Dr. Anderson (and which could be used to verify/authenticate the values in question) have (so far as can be determined) been lost or destroyed. In addition to the incomplete Ft. Snelling record, the Kelly record and the putative Anderson record, the 1858 east central Minnesota record includes temperature values recorded by several St. Paul pharmacists (records which have survived in fragmentary form and only to the extent published in pioneer era St. Paul newspapers).
Warm, cloudy rainy January: rain on 22, 23, 24, 26, 28 January. St. Paul newspaper [27 January] noted that "...with the thermometer varying at the temperate degrees, with three days of rain with the snow entirely washed from the hillsides and the level lands, with the mud three inches deep, with the river rising rapidly...all this in the middle of January...is it any wonder that people should...wonder what we are coming to...". Three to four inches of rain reported at the Princeton Mn station, 22-28 January. Cold February: readings of -21 F and -19 F at 0700 on 10, 22 February, respectively. Temperature of -23 F recorded at Morton's site at 0600 on 10 February. St. Paul newspaper accounts indicate that snow cover was about four inches on 21 February but that "after four or five days of warm. clear weather, the snow.....disappeared from the streets and about two inches of mud has taken its place..." [28 February]. Very warm, windy March: force five and force six winds indicated on many days. Reading of 68 F at 1400 hours on 15 March. Prairie fires noted on 19 March. St. Paul newspaper [16 March] contrasted March 1858 with the previous March by noting that "....a year ago the ground was covered with nearly twelve inches of snow...the ice on the river was from two to three feet thick...this year there is no snow on the ground...and the ice is only ten to twenty inches thick...". Cool, wet and very windy April: force eight winds on 4, 5 April; force seven winds 29 April. Force five and force six winds on many other days during the month. Rising river levels noted during April. Cool, wet May; few, if any, days with temperatures of 80 F or higher. Afternoon reading of 82 F at Ft. Ripley on 6 May. Wet June with much hot weather after mid-month: 100 F at Morton's site at 1200 hours on 17 June, 102 F at Princeton on the same date. St. Paul newspaper [5 June] indicated that "...so much rain has fallen this spring and water has been so abundant that half our population has become web footed....". Another account [11 June] stated that "the spring of 1858 has been one of the most remarkable...for a period of nearly two months, rain has been but briefly intermittent...the amount of rain must have been largely without precedent in a like period...the whole country has been drenched completely and the streams are unusually high...we had much damage done to property...". Destructive rain and wind storm in St. Paul on 8-9 July. Rising river levels noted on 15 July. Severe hailstorm in Faribault county on 30 July. Wet August with flooding and crop damage reported in much of southern Minnesota. "Unusually high stage of water" reported on the Mississippi river at St. Paul in mid-August. "The heaviest rains ever known in this country" were said to have fallen in many areas on 11-13 August. Cool late August: frost noted at the Princeton Mn station on 23, 28, 29 August: reading of 45 F at Morton's site at 0600 on 28 August. Cool and probably quite dry September. Cool October: first heavy frost of the season noted in St. Paul on 7 October. Falling river levels also noted during October. Heavy rains noted in mid-October. Cold mid-November: readings of 3 F, 3 F, 7 F and 2 F at Morton's site at 0600 on 15, 16, 18, 19 November, respectively. Reading of 0 F at Princeton station at 0700 on 19 November. Snowfall of 3.3 inches measured by St. Paul observer William Kelly on 12 November. Brief cold wave in early December: Readings of -25 F and -27 F at 0600 at Morton's site on 8, 9 December, respectively. Other St. Paul observers reported early morning readings from -25 F to near -30 F on 9 December: -32 F at Princeton on the same date. Snowfall of 2.5 inches recorded in St. Paul on 1 December, followed by 2.2 inches on 5 December and 1.7 inches on 7 December. Warm late December: St. Paul newspaper [30 December] indicated that "..there has been a thawing and rainy term of five days...which has liquified nearly all the snow on the ground...the effect on the river has been to weaken the ice...".