ANNUAL CLIMATOLOGICAL SUMMARY
FT. SNELLING MN
The 1837 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 1837 observations were taken within the Ft. Snelling enclosure (on the bluffs overlooking the confluence of the Mississippi and Minnesota rivers) .
The foregoing 1837 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 1837 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 1837 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 1837 and/or from notations entered in the remarks section of the 1837 record . The 1837 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 1837: 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 1837: 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.
Extant records indicate that significant, but unrecorded, precipitation fell on 4-5 February 1837: the foregoing precipitation for that month, accordingly, is considered to be incomplete.
Warm, dry and sunny January. Reading of 33 F at sunrise on 31 January. Prevailing winds from the west each day, 1-8 January. Warm, dry February. Reading of 33 F at sunrise on 14 February. Readings of 54 F and 50 F at 1400 hours on 19, 20 February, respectively. Cold, sunny and dry March. Reading of -12 F at sunrise on 14 March. Cold early April: reading of 6 F at sunrise on 3 April. Reading of 29 F at 1400 on 2 April. "Very severe snowstorm, lasting three days" noted, 4-6 April. Cool May: readings of 41 F, 47 F and 47 F at 1400 hours on 5, 8, 16 May, respectively. Rain and sleet on 2 May. Mixed rain and snow on 16 May. "Heavy" thunderstorm on 5 May. Rain with high winds on 8 May. Severe frost at the beginning of the month: 26 F at sunrise on 1 May. Reading of 30 F at sunrise on 17 May. Cool June: readings of 48 F at sunrise on 20, 25, 27 June; 60 F at 1400 on 26 June. Sunny July. "Heavy" thunderstorm noted on 17 July. Warm, humid conditions during late July. Cool, cloudy and dry August. "Heavy" thunderstorm on 15 August. Readings of 47 F and 42 F at sunrise on 22, 31 August, respectively. Cloudy, wet September: 3.2 inches of rain recorded, 14-16 September. Afternoon readings in the low 50's F each day, 15-18 September. Wet October. First frost of the season noted on 2 October. Sunrise readings in the low 20's F each day, 24-27 October. Reading of 60 F at sunrise on 17 October: 0.85 inches of rain recorded on that date. Warm, cloudy November. Most November precipitation was in form of rain: snowfall during the month was probably less than one-half inch. Wet, cloudy December. Sleet storm with 1.15 inches of meltwater and brisk northeasterly winds on 1 December. Heavy snowstorm, 8-9 December. Brief cold wave, 21-23 December: -22 F at sunrise on 22 December.