ANNUAL CLIMATOLOGICAL SUMMARY
FT. SNELLING MN
The 1839 Ft. Snelling climatological record consists of fixed time temperature readings taken daily at or about local sunrise (designated in the official record as the "AM" reading), 1400 hours local solar time (designated in the official record as the "PM" reading) and 2100 hours local solar time (designated in the official record as the "evening" reading); two daily entries indicating the prevailing direction of the wind and the general condition of the sky (expressed as "fair" or "cloudy"); a daily quantitative precipitation record (derived from measurements taken from the station's DeWitt rain gauge); intermittent records of snowfall and/or snow cover; episodic records of phenological, hydrological, astronomical and/or other natural events (windstorms, prairie fires, etc.); descriptive entries indicating the general duration (and, in some instances, the intensity) of precipitation; precipitation type ; and special atmospheric phenomena (fog, smoke, etc.). So far as can be determined, all 1839 observations were taken within the Ft. Snelling enclosure (on the bluffs overlooking the confluence of the Mississippi and Minnesota rivers) .
The foregoing 1839 temperature record includes both unadjusted (UNADJ) and adjusted (ADJ) mean temperatures. Unadjusted values are the averages of fixed time readings taken daily at sunrise and at or about 1400 and 2100 hours . 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 that would have been recorded had the Ft. Snelling station been equipped with self-registering thermometers read and re-set at midnight . The foregoing 1839 record also includes both the monthly and annual extreme temperatures (highest daily minimum, lowest minimum, etc.) estimated by Fisk and the monthly extremes actually recorded/observed (OBSRV) by fort observers. All 1839 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.
The foregoing "precipitation days" record is derived from quantitative precipitation records kept by fort observers during 1839 and/or from notations entered in the remarks section of the 1839 record . The 1839 record contains few quantitative snowfall values: the foregoing monthly snowfall values, accordingly, are estimates (obtained for the most part from National Weather Service meltwater-snowfall conversion tables) . Prevailing monthly wind direction is based on the air movement observations taken by station observers twice daily during 1839: prevailing monthly winds indicate the direction most frequently observed/recorded during any given month. Sky cover distributions, similarly, are based on observations taken twice each day during 1839: fair days are those with "fair" conditions noted at both observations; cloudy days are those with "cloudy" conditions noted at both observations: and "mixed" days are those with fair conditions noted at one observation and cloudy conditions noted at one observation.
Ft. Snelling precipitation record for January 1839 contains ambiguous/inaccurate entries. As a result, total January 1839 precipitation may be 1.34 inches, not 1.32 inches as indicated in the foregoing compilation.
Warm, cloudy January. Sunrise readings of 34 F, 36 F, 34 F and 35 F on 5, 6, 7, 9 January, respectively. Heavy snow, 27-30 January: 1.06 inches of precipitation recorded on those dates. Warm, cloudy February. Readings of 52 F, 50 F, 47 F, 50 F, 48 F and 49 F at 1400 hours on 12, 15, 20, 22, 23, 25 February, respectively. Brief cold wave early February: sunrise readings of -26 F, -25 F and -22 F on 1, 2, 5 February, respectively. Sunrise readings of 32 F, 36 F, 34 F, 35 F on 8, 14, 19, 20 February, respectively. Prevailing winds from the southern quadrant on eleven days during February. Cold early March: -16 F at sunrise on 3 March. Thunderstorm with hail on 12 March. Warm late March: readings of 68 F and 72 F at 1400 hours on 27, 31 March, respectively. Sunny, record warm April: afternoon readings in the 70's F each day, 1-6 April. Reading of 84 F at 1400 on 26 April. Sunrise readings of 51 F on 3, 4 April. Sunrise readings of 58 F and 61 F on 26, 27 April, respectively. Rainy late April: 1. 35 inches on 27 April. Heavy thunderstorm with 1.75 inches of rain on 7 May. Frost on 14 May: sunrise reading of 30 F on that date. Sunrise readings of 34 F on 15, 16 May. Dry, sunny June. Late June heat wave: 96 F recorded at 1400 on 30 June. Warm, sunny July. "Heavy" thunderstorm with two inches of rain on 19 July. Warm, sunny and dry August: readings of 96 F, 95 F, 97 F and 97 F at 1400 hours on 15, 19, 20, 27 August, respectively. Low river and lake levels noted during the summer of 1839. Dry, sunny September. Light frost noted on 10 September. Sunrise readings of 30 F and 28 F on 27, 29 September, respectively. Cloudy, warm October. Fifty degree rise in temperature noted during the forenoon and early afternoon on 3 October. Sunrise readings in the 60's F each day, 5-8 October. Heavy rain, 10-11 October: 1.65 inches recorded. Sunny November. Heavy rain with mixed snow, 4-5 November: 1.6 inches of precipitation recorded on those dates. Warm, cloudy December: sunrise readings above 32 F on most days, 1-7 December.