ANNUAL CLIMATOLOGICAL SUMMARY
FT. SNELLING MN
The 1842 Ft. Snelling climatological record consists of four daily fixed time temperature readings taken at or about local sunrise, 1400 hours local solar time: at or about local sunset, and at or about 2100 hours local solar time; wind and sky cover observations taken twice daily, probably at or about sunrise and at or about local sunset (or, alternatively, at or about 1400 hours local solar time); quantitative precipitation observations taken once each day, probably at or about local sunrise; 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 1842 precipitation values are from a conical DeWitt rain gauge. Also, so far as can be determined, all 1842 observations were taken within the Ft. Snelling enclosure (on the bluffs overlooking the confluence of the Mississippi and Minnesota rivers) .
The foregoing 1842 temperature record includes both unadjusted (UNADJ) and adjusted (ADJ) mean temperatures. Unadjusted values are the simple averages of fixed time readings taken daily at sunrise, 1400, sunset 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 1842 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 1842 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 frequency record (e.g. number of days with snow, etc.) is from quantitative precipitation records kept by Ft. Snelling observers during a 1842 (a record which, however, is supplemented by descriptive remarks in the station's monthly meteorological register) . Because the original 1842 record contains no quantitative snowfall data, the foregoing monthly snowfall values are estimates (obtained in most instances from National Weather Service meltwater-snowfall conversion tables) . Prevailing monthly wind values are based on entries indicating the direction of the wind as recorded by station observers on the morning and afternoon/evening of each day during 1842. Prevailing monthly winds indicate the direction most frequently observed/recorded during any given month. Sky cover distributions are based on observations taken twice daily during 1842 : 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.
The Ft. Snelling station's October 1842 precipitation record indicates that NO rain or snow fell on any day during that month. In fact, however, it is likely that several small (but unrecorded) precipitation events occurred during the month, perhaps depositing a trace (T) to as much as 0.05 inches of moisture. The June 1842 precipitation record includes several ambiguous/semi-legible values: as a consequence, total precipitation for that month could be 4.33 inches (rather than 3.73 inches as indicated in the foregoing annual climatological summary). Extant 1842 records indicate that NO snow fell during March 1842: it is probable, however, that snow flurries and/or very small amounts of snow fell on several days early in the month. Extant evidence also suggest that the precipitation record for the months of January, June, September and December 1842 may be incomplete: remarks entered in the station's meteorological diaries indicate that observers failed to measure small amounts of precipitation which fell on one or more days during these months.
Sunny, warm January. Very warm mid-January: reading of 49 F at 1400 hours on 17 January. Heavy snow on 8 January . Warm, sunny and probably relatively snowless February. Very warm early February (with afternoon readings near 50 F on 2, 3 February) and again late February. Rain on 28 February. Dry, very warm and sunny March. Reading of 73 F at 1400 on 18 March. Buds on poplar trees open on 25 March. Warm, sunny, windy April. Reading of 86 F at 1400 on 21 April. Reading of 58 F at sunrise on 2 April. Work on fort gardens commenced on 15 April. Very cool May. Heavy frost with readings of 28 F at sunrise on 3, 4 May. Sunrise readings of 36 F on 24, 29 May. Dry, sunny early May with no rainfall recorded, 1-11 May. Reading of 43 F at 1400 on 12 May. Hail and high winds on 29 May. Record cold June: sunrise readings of 40 F, 39 F, 40 F, 41 F, 42 F, 38 F, 40 F and 42 F on 6, 10, 13. 17, 18, 19, 20, 27 June, respectively. Afternoon readings of 57 F, 52 F, 54 F, 50 F, 62 F, 62 F and 60 F on 10, 11, 16, 18, 28, 29, 30 June, respectively. Northwesterly and northeasterly winds predominate on most days during the month. Thirty minute rainfall of 1.5 inches noted on 21 June. Cool, windy July. Sunrise readings of 47 F, 41 F, 46 F, 46 F and 48 F recorded on 1, 5, 6, 8, 14 July, respectively. Afternoon readings of 64 F, 60 F, 57 F, 58 F, 63 F and 65 F on 1, 2, 3, 7, 30, 31 July, respectively. Cool, wet August. Rain beginning at about 2200 hours on 16 August, continuing "constantly" for twenty four hours: 3.15 inches recorded. Sunrise reading of 46 F on 1 August. No precipitation recorded, 1-15 August. Wet early September. "Tremendous thunderclap" noted during the night of 25 September. Sunny, very dry October. Smoky conditions caused by prairie fires noted on the last ten days of October, 25-26 October in particular. Warm late October: afternoon reading of 67 F on 31 October. Wet, cloudy and very cold November: sunrise readings of -4 F, 6 F, 0 F, -17 F and -12 F on 16, 17, 21, 27, 28 November, respectively. Afternoon readings of 9 F, 0 F, -6 F and 0 F on 16, 26, 27, 28 November, respectively. Warm conditions during the first week of November. Cloudy, seasonal December with very dry conditions, 1-28 December.