FT. SNELLING MN
The 1821 Ft. Snelling climatological record consists of fixed time temperature readings taken daily at or about 0700, 1400 and 2100 hours local solar time; single daily entries indicating the prevailing direction of the wind and the general condition of the sky; 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, observations were taken at Cantonment New Hope (a temporary camp consisting of log huts constructed in 1819 in the bottomlands adjacent to the St. Peter's [Minnesota] river) during the early months of 1821. During the remainder of the year, records may have been kept at Camp Coldwater, a temporary summer camp site on the upland prairie about one mile northwest of the site of the permanent fort enclosure and/or within the permanent fort enclosure on the bluffs overlooking the confluence of the Mississippi and Minnesota [then the St. Peters] rivers .
Because they were obtained from instruments exposed in the Minnesota river bottomlands, temperatures recorded during the first several months of 1821 are undoubtedly significantly lower than values which would have been obtained (ceteris paribus) from thermometers located at the Ft. Snelling or Camp Coldwater sites (both of which are significantly higher than the bottomlands site). Analysis of the relationship between 0700, 1400 and 2100 readings further suggests that station thermometers -- at least during the summer months -- may have been exposed to the direct rays of the early morning and/or the mid-afternoon sun. This suggests, in turn, that average temperatures during the summer of 1821 may have been significantly lower than those indicated in the "official record" .
The foregoing 1821 temperature record includes both unadjusted (UNADJ) and adjusted (ADJ) mean temperatures. Unadjusted values are the averages of fixed time readings taken daily at 0700, 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 are based on 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 1821 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 1821 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.
Although no quantitative precipitation records were kept at Ft. Snelling during 1821, extant records do, as noted, contain entries indicating precipitation type and, in some instances precipitation intensity (e.g. light snow, heavy rain, etc.). These records are the basis of the foregoing 1821 precipitation frequency record (e.g. number of days with snow, etc.) . Prevailing wind values, similarly, are based on entries indicating the predominate direction of the wind on each day of the month. Prevailing monthly winds indicate the direction most frequently observed/recorded during any given month.
Cold but relatively cloudy January (fifteen days during month described as "cloudy"). Temperature of -32 F at 0700 hours on 24 January. Temperatures near -30 F probable on 3 January. Cold late February following mid-month warm-up. Temperature of 46 F recorded at 1400 hours on 18 February: 37 F at 0700 hours on 19 February. Rain and hail during the night of 9-10 February. Two inches of snow on 8 February. Windy March. Cold mid-March: 16 F recorded at 1400 hours on 17 March, Cold April. Four inch snowfall noted on 14 April. Thirteen "cloudy" days recorded. Cool May with probable frost at mid-month. Heavy rain on 27 May. Warm June: 98 F recorded on 11 June. Fourteen days during month recorded as "cloudy". Heavy rain on 8 July. Temperature of 65 F at 1400 hours on 11 July. Very warm but relatively cloudy August (fifteen days during month recorded as "cloudy"). Heavy rain on 2, 27 August. Fifteen "cloudy" days recorded during September. Light frost noted on 21 September (probably in low lying areas only: 46 F recorded at 0700 hours on that date). Heavy frost on 26 September. Warm, pleasant late October: 72 F at 1400 hours on 26 October. Twenty one "clear" days recorded during October. Rain and snow on 31 October. Cloudy November. Very cold December. Eight inch snowfall noted on 2 December. Very cold mid-December; -22 F at 0700 hours on 23 December. Fourteen "cloudy" days during December.