MINNEAPOLIS-ST. PAUL AREA DAILY CLIMATOLOGICAL HISTORY OF TEMPERATURE, PRECIPITATION,
AND SNOWFALL, A YEAR-BY-YEAR GRAPHICAL PORTRAYAL (1820-PRESENT)
By Charles Fisk*
The following series of links comprise a year-by-year visual time-series history of Minneapolis-St. Paul area daily temperatures, precipitation, and snowfall, from the beginning of continuous daily record keeping at old Fort Snelling in 1820 to present day observations at the Minneapolis-St. Paul International Airport. The graphs can be used for historical reference, descriptive climatology, or browsed for their own sake. The history includes more than 38 years’ observations through early 1858 at Fort Snelling, another 14 years of St. Paul Smithsonian Institution volunteer recordings (1859-1872), followed by a century-and-a-quarter of government weather service observations in St. Paul (1873-1890), downtown Minneapolis (1890-1938), and the current Minneapolis-St. Paul Airport location (1938-present). The current year’s graph is updated monthly. Preceding the year-to-year graphs are a set of eleven summary overview charts, plus a link to year-by-year accounts of early Minnesota weather history for the 1820-1869 era.
- GRAPH TYPES DISPLAYED
Six types of graphs are presented: 1) daily maximum and minimum temperatures, 2) daily mean temperature departures from “normal” (daily mean temperatures less climatological mean temperature for the day), 3) standardized daily temperature departures from average (departure statistics of (2) divided by the standard deviation of daily means for the day), 4) daily precipitation totals (from 1836), 5) daily snowfall totals (from 1891), and 6) daily snow depths (from 1893).
- THE DATA: OFFICIAL WEATHER BUREAU OBSERVATIONS AND RECONSTRUCTED PIONEER ERA RECORDINGS
Temperature graphs for the 1873 to present period are based on official St. Paul or Minneapolis weather bureau observations of twenty-four hour absolute maximum and minimum temperatures for a given day (nearly all for the midnight-to-midnight period), the standard method of recording "summary-of-the-day" temperature statistics for first-order weather stations.
Original daily temperature statistics for the 1820-1872 “Pioneer” period consisted of fixed-time scheme temperature observations, along with those of sky cover and wind direction/force, according to a prescribed format (for example: at 7AM, 2PM, and 9PM; or Sunrise, 9AM, 3PM, and 9PM). To conform to the first-order-station temperature observation method, “homogenize” the entire record in this regard, and in the process permit identical-type day-to-day temperature graphs throughout, the 1820-1872 daily observations were transformed into midnight-to-midnight maxima and minima estimates. This was accomplished by application of statistical models that defined 1961-1980 empirical relationships between Minneapolis-St. Paul Weather Service Office temperature, cloudiness, and wind information at hours corresponding to the old fixed-time schemes, and 1961-1980 midnight to midnight temperature maxima and minima [Fisk, 1984]; see http://climate.umn.edu/pdf/Fisk_thesis.pdf.
- HETEROGENEITY OF THE CONSOLIDATED RECORD
In addition to the use of statistically estimated daily maxima and minima for the first 53 years, the temperature series presented here reflect differing exposure techniques (e.g., open-air for the thermometers in the pre-weather bureau era), varying instrumentation qualities, site relocations, and environmental changes associated with urbanization.
The Minneapolis-St. Paul area data are based on materials originally obtained from the National Archives, the Minnesota Historical Society, The University of Minnesota Periodicals Library, the National Climatic Data Center, the Minneapolis-St. Paul National Weather Service Office online site, and the Minnesota Climatology Working Group. Monthly updates are based on data from the site: http://climate.umn.edu/doc/prelim_lcd_msp.htm
The uppermost chart on a given yearly page are “floating-bars” of the daily maxima and minima. Each bar represents an individual day’s temperature range. Superimposed are two line traces, the upper one connecting average daily maxima, the lower one average daily minima. The bars depict the varying diurnal, synoptic, long-wave, and seasonal influences on temperature over time, and on a subjective basis, the features for some years can be quite striking (see “LINKS TO SOME OF THE MORE INTERESTING YEARS WITH ACCOMPANYING NOTES” section below).
The second chart down shows the arithmetic departures of day-to-day mean temperatures (sum of the daily maximum plus the daily minimum divided by two) less the corresponding calendar-day average means. Vertical lines extending upward from the zero line indicate above average means for the day (colored red), those extending downward indicate below average daily means (colored blue). In the entire series of nearly 68,000 days, greatest positive departure for any individual day is +38 F for 25 January 1944, the greatest negative departure -45 F for 1 January 1864.
The third chart down shows chart two’s departures in deseasonalized or “standardized” form. This adjusts for the fact that individual calendar days have higher or lower inter-year variability in mean temperature. For example, inter-year variability (or standard deviations) of same-day daily mean temperatures for the 1820-2006 period ranged from 14.87 F (4 February) to 5.48 F (21 August). Dividing by these calendar day standard deviations deseasonalizes the arithmetic departures, and creates the standardized departures or “z-scores”. Anomalies of greater than or equal to 2.0z (both positive and negative) are observed about 4.0% of the days (or about 15 such events on average over the course of a year); those of plus or minus 2.5 or greater occur on about 0.8% of the days; or minus 3.0 events just 0.1%. Only five daily departures in the entire series are plus or minus 3.5 or greater. Three of these, all negatives, came over the four-day period 4-7 November 1991, associated with an unseasonably cold arctic air outbreak in the wake of a record early and heavy snowstorm.
The fourth chart down depicts daily rainfall, the fifth and sixth charts, respectively, showing daily snowfall and snow depths.
- LINKS TO SOME OF THE MORE INTERESTING YEARS WITH ACCOMPANYING NOTES
1824-1825 – (July-June view). Exceptionally mild December ‘24 to April ’25 period; likely El Nino influence.
1829 - “The Dry Year”, as described by early Minnesota history texts. Severely cold February and other extreme temperature spells throughout year.
1830 - Hottest July until 1936, and much above normal October/November.
1833 - El Nino winter of ‘32-’33 mildest for another 45 years. Very mild December ’33 also.
1833-34 - (July-June view). Greatest three-month thermal “see-saw” in history: January 1834 29 F colder than December 1833, February 1834 28 F warmer than January.
1835 - Volcanic dust-veil produces series of anomalous cold spells during second half.
1838 - Great temperature extremes. Minus 40 F in February and a hard freeze in late May. Hot summer, but unseasonable cold in fall and early winter.
1838-39 - (July-June view). Abnormal cold over October to December ’38 gives way to abnormal warmth over January to April ‘39.
1839 - Warmest recorded year up to this time; warmest April down to the present day.
1842 - Extraordinary persistent coolness over mid-May into July (June snow observed back East in Cleveland). Coldest June and coldest November in all history down to present.
1842-43 - (July-June view).
1845 - Steep temperature plunge over mid-to-late November.
1846 - Warmest year of pre-statehood era. Mildest January in all history down to the present .
1849 - December 34 F colder than November.
1855-56 – Two successive arctic sieges over late December and early January Another in February.
1857 - Second successive bitter winter. Coldest January and April in history.
1863 - The “Strange” weather year. Extremes in temperatures, and worst growing season drought in area history up to this point - no measurable rain in June (St. Paul). Killing frosts in July and August across settled areas.
1864 - Continued drought during the year. Frigid New Years’ Day – Maximum: -24 F, Minimum: –38 F in St. Paul.
1865 - Heavy summer rains break drought; 38” recorded for year in St. Paul, more than ’63 and ’64 combined. Very cool summer, July 1 F cooler than September.
1867 - Very backward spring. March 1867 5 F colder than any March since, but still 8 F warmer than 1843. More than 10” rain in June in St. Paul.
1869 - More than 18” rain over August and September.
1877-78 - “Year Without a Winter”. El Nino-induced extraordinarily mild winter. Mildest December in history. Near record warmest February and March.
1879 - “Second Edition of Summer” brings unseasonable October warmth. Very cold Christmas Day, however, minus 39 recorded in St. Paul.
1885 - Great temperature variability over January to March.
1888 - Severe winter (including –41 F in January). Persistent spells of unseasonable coolness into spring and summer.
1895 - Abrupt May cold turn temporarily derails an otherwise forward Spring.
1899 - Great February cold wave.
1907 - Persistent abnormal cold through April and May; 13” snowstorm over Apr 27-28.
1910 - Driest year (11.54”) in local climatic history down to present. Also warmest March in all history.
1911 - Great adjacent-year reversal in annual precipitation – Wettest year (40.15”) in all history down to present.
1915 - Very forward April, but May 4 F colder; very cool summer ensues.
1917 - Coldest year of 20th Century. Deep Snows – 31” depth on 16 March.
1921 - Warmest year since 1878.
1923 - Very cold March, very mild November-December.
1930 - Sharp temperature gyrations over latter part of year.
1933 - Warmest June in history. 77 F on 1 November
1934 – In midst of Dust Bowl era. Warmest May in history, including 106 F on the 31st. June registers a 104 F day, three days in July record 105 F.
1936 – Great temperature contrasts between winter and summer. Thirty-six consecutive days with subzero minima over January and February (including –34 F in January). Hottest July on record; 108 F recorded on 14th for highest in history. Also recorded in July: 106 F three times, 105 F and 104 F once each.
1940 – Great Armistice-Day Blizzard leaves nearly 17 inches’ snow over 11th-12th.
1942 – Highly irregular temperature anomaly pattern over course of year.
1945 – Very forward early spring, then very cool through early summer.
1947 – Warmest August AND October in all history down to the present.
1948 - March temperature range –27 F to 70 F (97 F spread highest ever for a single calendar month locally).
1951 – 40” snowfall in March.
1953-54 – Very visual quasi-periodic much above normal spells over late-August through February. February ‘54 a near record warmest.
1958 - Driest year (16.20”) since 1910.
1959 – December 5 F warmer than November.
1962 - Deep snows in late February and early March; minus 32 F on 1 March.
1965 - Coldest March since 1899; coldest September since 1868.
1967 - 35.3” snowfall in January; 30” snow depth on 19 February.
1972 - Coldest year since 1917.
1976-77 – Twentieth century version of 1838-39: Abnormally cold October-January, unusually warm February-May.
1982 - 46.4” snowfall in January, 38” snow depth on 23 January. 1981-82 season sets new snowfall record (95.0”) – only to last two seasons, however.
1983 - Wettest year (39.07”) since 1911. Very mild January to early March, a warm summer, but coldest December since 1831. 21.8” snowfall in April – a new high mark for that month.
1983-84 - Snowiest winter in history (98.4”).
1985 - Unusually mild March and April, cold November-December.
1988 - Drought year. Very hot summer, 105 F in July.
1991 - Great early snowstorm drops 27” over 31 Oct and 1 Nov followed by unseasonably early arctic outbreak; 46.9” total snowfall for November, snowiest calendar month in recorded history.
1992 - Very mild winter. Very cool summer (possibly induced by Mt. Pinatubo eruption); Coolest July since 1865.
1996 - Great arctic outbreak in late-January/early February.
1997-98 - El Nino-induced, very mild ‘97-‘98 winter.
2000 - Very mild March, very cold December.
2001 - Wettest April on record (7.00”). Warmest November in history by more than 4 F. Fifty-seven consecutive above normal temperature days from late October to late December.
2001-02 - Mildest November-February period in all history by nearly 2 F.
*Member, American Meteorological Society Last Update: 2 May 2007