ANNUAL CLIMATOLOGICAL SUMMARY
FT. SNELLING MN
The 1850 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; two daily fixed time wet bulb readings; 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) . 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. Wet bulb readings were taken at local sunrise and at 1500 hours local time. Although extant records give no explicit indication of the time at which 1850 precipitation observations were taken, contextual evidence suggests either a 2100-2100 schedule and/or an early morning (probably "sunrise") schedule (which, in at least in some instances, may have entailed "shifting" of precipitation values from the date on which the observation was actually made to the day immediately preceding).
So far as can be determined, 1850 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 several notable exceptions (as discussed below), fixed time temperature readings taken during 1850 are consistent with "normal" diurnal patterns (indicating that the station thermometer was, for the most part, located/sheltered as necessary to protect it from the direct rays of the sun).
All 1850 wind force values are expressed in terms of a numeric wind force value selected by fort observers after visually noting the effect of wind on flags, trees, signs and other easily movable objects . The degree of cloudiness was similarly quantified, using a scale of zero (complete overcast) to ten (a totally cloudless sky) . However, unlike records from 1849 and several prior years, the 1850 record contains NO notations indicating the total number of "fair" and the total number of "cloudy" days observed during each month of the year: for reasons not indicated in extant records, this entry was dropped from the station's monthly meteorological register, beginning in January 1850. Also, in contrast to sky cover records from 1849 and several years previous, 1850 Ft. Snelling sky cover values appear to provide a reasonably accurate/reliable record of cloudiness (probably because "hazy" and/or "smoky" days were no longer recorded as "cloudy" days and/or because sky cover observations were taken more carefully/rigorously than in the past).
Unlike the 1850 daily sky cover record (which includes a complete set of daily entries), the 1850 force of wind record is typically incomplete: air movement records include a significant number of wind direction entries UNACCOMPANIED by corresponding numeric 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.
Like corresponding records from preceding years, the 1850 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" or "slight" to denote small, but perhaps otherwise measurable, amounts of precipitation). This tendency is particularly evident in the December 1850 (and, to a lesser extent in the November 1850) precipitation record: St. Paul newspaper accounts of 1850's early winter weather (including accumulated snow depth) suggest that Fort observers, for whatever reason, failed to measure or record (or even note) much of the snow which fell from mid-November through the end of December. The result is a December 1850 meltwater value (0.04 inches) so unrepresentative/specious as to impugn the entire precipitation record for that month .
Although the 1850 Fort Snelling record includes daily liquid/melted precipitation values and a record of the TYPE of precipitation observed, it includes NO QUANTITATIVE snowfall values (whether of fresh snowfall or accumulated snow cover). The January-May snowfall values in the foregoing compilation are, accordingly, estimates obtained by applying the National Weather Service meltwater-snowfall conversion matrix to the liquid precipitation values recorded on which snow was noted (and/or on days with temperatures low enough to preclude rain or drizzle). The foregoing snowfall values for November-December 1850 are from the records of St. Paul observer J.W. Bond (whose records, as published from time to time in St. Paul's pioneer era newspapers, sometimes included daily and monthly snowfall data) .
In addition to outdoor temperature, sky cover, precipitation and air movement data, the 1850 Ft. Snelling record includes four daily readings taken from the station's mercury barometer and from the "attached" thermometer (readings which, as noted above, were probably used to correct barometric readings for the effects of temperature on the mercury in the station barometer). So far as can be determined, 1850 barometric values are station pressures (i.e. readings which have not been adjusted to compensate for elevation above mean sea level).
Analysis of the 1850 Ft. Snelling record reveals that the 1850 temperature record (like temperature records for several years in the mid-1840's) may have been compromised by improper instrument exposure and/or erratic observational schedules. Specifically, fixed time temperature readings taken during the warm months of 1850 show 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 mid-morning rays of the spring and summer sun and/or that observations were often taken at times significantly different than the times indicated in the official record .
The foregoing 1850 climatological record includes both unadjusted (UNADJ) and adjusted (ADJ) mean temperature values. The unadjusted record, in turn, includes two monthly mean temperature values: a) the simple average of fixed time readings taken daily at sunrise, 0900, 1500 and 2100 hours; and b) the simple average of fixed time readings taken daily at sunrise, 1500 and 2100 hours ONLY. Because it disregards the often anomalous 0900 hour readings, the second set of unadjusted averages illustrates the extent to which sun contamination may have distorted the 1850 Ft. Snelling temperature record. 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 1850 record also includes both the monthly and annual extremes (highest daily minimum, lowest minimum, etc.) estimated by Fisk and the monthly extremes actually recorded by fort observers. All 1850 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 and/or force of wind values are the simple average of the station's four daily numeric sky cover and wind velocity entries. The foregoing prevailing wind values are based on daily entries indicating the direction of the wind at sunrise/0900/1500/2100: prevailing/predominate winds are those most frequently observed/recorded during any given month.
Precipitation during July 1850 may have totaled 6.15 inches (rather than the 6.17 inches indicated in the foregoing compilation): the station's 19 July 1850 precipitation entry cannot be satisfactorily/definitively deciphered.
In addition to the Ft. Snelling record, the foregoing 1850 climatological record includes a summary of temperature records kept during December 1850 by St. Paul observer J.W. Bond (and as published in pioneer era St. Paul newspapers). This record is from self-registering thermometers which were read and re-set at dawn. So far as can be determined, the December record is the only surviving portion of a more complete set of records kept by Bond during 1850. Bond's station coordinates were given as 44:56 N and 93:05 W.
Cold early January with moderate temperatures during much of the remainder of the month: reading of 36 F at sunrise on 10 January. Readings at low as -28 F recorded in St. Paul at the beginning of January. Heavy snow during January: "very severe" snowstorm beginning at about 1100 hours on 20 January, continuing until 22 January (total snowfall of about ten inches reported in St. Paul). Force five and six winds recorded on 21 January. Force seven winds on 11, 14 January. Record suggests that January was an abnormally cloudy month. Brief cold wave early February followed by generally moderate temperatures during the remainder of the month. Mixed snow and rain accompanied by force seven winds on 28 February. Cold, snowy March. Heavy snow on 12 March: blizzard on 17-18 March. Sunrise readings of 7 F, 4 F, 4 F and 6 F on 23, 24, 25, 26 March, respectively. Windy, cloudy and very cold April. Force nine winds on 12 April. Very wet early April. Prairie fires noted on 5, 12, 15, 22, 23, 25 April: "prairies on fire in all directions" on the latter date. Afternoon readings of 30 F, 28 F, 32 F, 41 F and 41 F on 12, 13, 15, 29, 30 April, respectively. Local flooding during April, largely the result of upstream snowmelt (northern Minnesota reportedly experienced very heavy snowfall during the winter of 1849-50). Windy, very dry May. Afternoon readings in the 40's F each day, 3-10 May. Prairie fires noted on 11, 12, 14, 15, 16 May. Warm, wet June. Heavy thunderstorm accompanied by force nine and force ten winds on 17 June. Wet, very warm July. Excessive rains on 30 June-1 July. Sunrise readings of 79 F, 84 F, 80 F and 83 F on 5, 9, 10, 26 July, respectively. Afternoon readings of 97 F and 98 F on 16, 24 July, respectively. Extensive and serious flooding of many Minnesota rivers during the summer of 1850: record flooding noted in the Red River Valley. Local flooding on the Mississippi and Minnesota rivers. Warm, humid August. Sunrise readings in the 70's F each day, 1-4 and 7-18 August. Afternoon reading of 62 F on 31 August. Mild, sunny September. Light frost noted on 17, 19, 28 September. Mild, very dry and sunny October. Prairie fires noted on 27-28 October. Warm November. Heavy rains, 3-4 November. "Smoky and dark during the day as a result of prairies being on fire" on 9 November. Prairie fires also noted on 22 November. Cold December: very cold, 3-7 December. Force seven winds on 2 December. Snowstorm with four inches of snow on 8 December. Sleighing "good" in St. Paul until 21 December. No recorded temperatures above 32 F during the entire month of December.