ANNUAL CLIMATOLOGICAL SUMMARY
FT. SNELLING MN
The 1854 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) . 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. Although extant records give no explicit indication of the time at which 1854 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, 1854 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 summer readings taken at 0900 hours, fixed time temperature readings taken by Ft. Snelling observers during 1854 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 1854 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 . The degree of cloudiness was similarly quantified, using a scale of zero (denoting a totally cloudless sky) to ten (a completely overcast sky).
Unlike the 1854 daily sky cover record (which includes a complete set of daily entries), the 1854 force of wind record is often incomplete: several air movement records include wind direction entries UNACCOMPANIED by corresponding Beaufort 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 the years immediately preceding, the 1854 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 1854 record itself -- suggest, in fact, that Fort observers, for whatever reason, failed to measure or record some portion of the precipitation which fell during the winter months (and, to a lesser extent, probably the summer months as well).
Although the 1854 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 1854 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 1854 "snow days".
As noted previously, the 1854 Ft. Snelling record includes four daily readings taken from the station's mercury barometer and from the "attached" thermometer (readings which, also as noted above, were probably used to correct air pressure readings for the effects of temperature on the mercury in the station barometer). So far as can be determined, 1854 barometric values are station pressures (i.e. readings which have not been adjusted to compensate for elevation above mean sea level).
Analysis of the 1854 temperature record suggests that many summertime temperature readings taken at 0900 hours may have been compromised by improper instrument exposure and/or erratic observation schedules. Specifically, fixed time temperature readings taken during the warm months of 1854 suggest an inordinate "compression" of 0900 and 1500 hour values. This suggests, in turn, that the station thermometer was 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 1854 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 or about sunrise, 0900, 1500 and 2100 hours; and b) the simple average of fixed time readings taken daily at sunrise, 0900 and 2100 hours ONLY. Because it disregards the often anomalous 0900 readings, the second set of unadjusted averages illustrates the extent to which sun contamination may have distorted 1854 temperature records. 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 1854 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 1854 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 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 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.
The amount of precipitation officially recorded by fort observers during January and October 1854 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. Precipitation recorded during February, April and June 1854 may have totaled 0.03 inches, 2.51 inches and 3.31 inches, respectively. Original precipitation records for these months contain several unclear and/or erroneous entries.
Very cold January: sunrise readings of -36 F, -32 F, -28 F and -26 F on 21, 22, 23, 24 January, respectively. Afternoon reading of -17 F on 22 January. Twelve inch snow cover noted on 28 January. St. Paul newspapers noted that several days in late January were "the coldest days experienced..for many years...At. Ft. Ripley the mercury remained frozen for thirty six hours and water froze in wells twenty five feet below the surface...In St. Paul the mercury fell from 36 to 40 degrees below zero...". Rapid late January warm-up with afternoon reading of 45 F on 31 January. Windy, very dry February: force seven winds on 22 February. Winter snow cover dissipated by late February thaw (23 February St. Paul newspaper noted that "sleighing in the city has nearly disappeared..."). Temperature of -17 F at sunrise on 17 February, rising to 35 F at 1500 hours. Windy March: force eight winds on 2 March, force seven winds on 3 March. Extensive prairie fires noted on 10, 12, 14, 15, 16, 18, 24, 25, 29 March. "Very low" water levels in the Mississippi and Minnesota rivers on 17 March. Cold early April: readings of 28 F and 9 F at 1500 on 1 April and at sunrise on 2 April, respectively. Rapid early April warm-up: 76 F at 1500 on 5 April. Warm late April: afternoon readings of 85 F and 86 F at 1500 on 19, 20 April, respectively. St. Paul newspaper [26 April] noted that "during the past ten days, the weather has resembled that of June...the thermometer ranging from 75 to 90 degrees in the shade...". Cloudy, wet, windy May: force seven winds on 8, 16, 17, 18 May with force six and force five winds on many other dates. Prairie fires noted on 2, 4, 7 May. Excessive rains, 16-17 May: 2.7 inches recorded at Ft. Snelling. St. Paul newspaper [17 May] noted that "...the storm continues to rage with increased fury...the rain commenced on Tuesday morning and has continued without a moment's abatement to fall in torrents ever since...it is accompanied with a stiff breeze from the north...". Warm June but with cool conditions on several days during the early part of the month: readings of 50 F and 41 F at 1500 hours on 6 June and 41 F at sunrise on 7 June, respectively. Warm July. "Severe" thunderstorms noted on 24, 27, 29 July. Damaging lightning strike near fort on 18 July. Damaging thunderstorm in St. Paul on 4 July. Warm August: afternoon readings of 92 F, 95 F, 94 F, 90 F, 91 F and 95 F on 20, 21, 22, 23, 24, 28 August, respectively. Temperatures near 100 F reported in St. Paul in late August. Severe thunderstorms 1, 31 August. Warm, wet September. "Slight" frosts noted in outlying areas on 12 September. Rising river levels noted during September. Warm October: afternoon readings of 70 F on 24, 26, 27 October. Smoky conditions on 5, 6 October. Prairie fires noted on 27, 31 October. St. Paul newspaper [2 November] noted that "...the western sky was all illuminated and the bright and ever changing line of the fire extended for miles...". Mild November: St. Paul newspaper [23 November] noted "...here it is, the 23rd of November and we are enjoying..fine Indian summer weather...". Weather in late November was said to be "comfortable in sitting rooms..without a fire...". Little or no snow cover at any time during November. Warm December: reading of 34 F at sunrise on 27 December. Sleighing said to be "measurably good" on 19 December.