Minnesota (Fort Snelling) weather for the year 1847

Much Cooler, Dry Winter and Fall (graphic)

Thermal patterns at Fort Snelling returned to generally cool again for 1847, annual mean temperature at the Post dropping 7 F to 42 F, a tie for second coldest in 28 years’ history. January and March combined were 20 F colder than a year ago and May was not unlike its wet and backward ’42, ’43, and ’44 predecessors. Except for a brief heat wave in early July, the summer was also marked by persistent coolness. Fall, however, had some record-breaking individual days’ heat in October and November. Thanks to an exceedingly dry January-April period along with October, total annual precipitation (about 22 inches) was the least in eight years.

Cold January and March – December’s mild/overcast pattern gave way abruptly to bitter cold over the first days of the new year, January (mean temperature: 4 F) to be the coldest calendar month in four years. Snowfall was light, about 3 inches total. On the 6th, the year’s first arctic invasion set in over the area, the Snelling thermometer -11 F at sunrise, start of a six-day spell with mid-afternoon observations never higher than 2 F, morning readings as cold as minus 21. Fresh arctic impulses continued to invade all through January and into early February, -22 F recorded on the January 16th, -24 F on both the 18th and 21st, and -22 F on the 27th. Most wind forces during the coldest episodes, however, were light. Following -16 F on the morning of 3 February, the flow from the northwest was at last shut off and a gradual warming trend developed. No more subzero mornings would occur during February (mean temperature: 19 F), thawing afternoon temperatures being the rule after mid-month. A couple of afternoons reached the low 40’s. Just one inch of snow fell during February, the winter’s accumulation at month-end a paltry 5 inches or so. The stage now seemed set for another early breakup of the rivers, but conditions instead did a wintry relapse over early March. First, a series of light snows dropped 4-5 inches, creating the deepest covering of the winter. Next a ten-day cold snap set in, bringing a number of subzero mornings, as low as minus 12 F on the 11th. Below zero cold was felt as late as the 16th, but then, spring-like weather suddenly burst over the area, afternoon readings reaching the mid-50’s on both the 18th and 19th. The last days of the month featured some wildly gyrating temperatures, not unlike two years ago about this time. Only 28 F was reached on the afternoon of the 25th, but three days later the mercury soared to 74 F, the 30th, however, just 32 F. With only .01 inch of precipitation having fallen since the first week’s snows, prairie fires were burning in “every direction” on the 26th and “extensively” to the south and west on the 28th. Despite the moderating readings after mid-month, monthly mean temperature (23 F) was still the second coldest for a March in ten years.

Mild/Dry April, Wet/Cold May – April (mean temperature: 46 F) continued the scanty precipitation pattern with just three falls totaling one-half inch. The first half was cool to seasonable with most afternoons in the 40’s and 50’s, a notable exception being 76 F on the 11th. Ice finally started to run in the Mississippi on the 3rd, the river clear on the 8th. Lake Pepin opened the day before. A brief late cold snap brought high winds, light snow, and afternoon temperatures around freezing on the 17th and 18th, but just a week later the mercury was in the summery low 80’s for three straight afternoons. On the 24th-29th, the atmosphere was reported “smokey”. May once again presented a major relative contrast to April with frequent rains, clouds, and much cooler than average temperatures. Fourteen days had rain, totaling 4.96 inches, ten of these over the last fifteen. Average clearness of the sky was just 2.1, and monthly mean temperature (52 F) tied 1843 for second coolest in 28 years. Just one afternoon was warmer than 80 F, most of the others in the 50’s and 60’s. An early Minnesota history text reports that the first attempted log drive on the Rum River was attempted this year, all of the logs, however, lost “on account of high water” [Ford and Johnson, 1961]. Perhaps it was during this rainy May that the unfortunate event occurred upstream of St. Anthony Falls.

A Single Summer Hot Spell – Summer ’47 was much like ’42, ’43 and ’44 with unseasonable coolness lingering into June. Virtually all the summer’s hot weather was confined to a single spell in July. Overcast and cool weather featured June through mid-month (mean temperature for the month: 65 F), a turn to warm and humid coming over the latter part. Rainfall was less frequent and intense than May’s, 2.66 inches recorded on ten days. Average clearness of the sky for the first sixteen days was a dreary 1.8, most afternoons confined to the 60’s or lower, a number of mornings in the 40’s. The 13th had only 56 F at 3PM accompanied by force 5 northerlies (35 miles per hour). The following morning was 43 F at sunrise, for the month’s coolest temperature. Behind persistent east to southeasterly winds, a moderately warm (and humid) pattern set in over the last ten days, afternoon temperatures frequently in the mid-80’s, overnight temperatures holding in the mid-60’s. July (mean temperature: 72 F), presented the summer’s only oppressive spell, over the 7th-16th. Rainfall was increased from June, 3.66 falling on 14 days, 2.81 inches of this over the first sixteen. Daily temperature ranges over the 7th-16th averaged 72 F at sunrise and 87 F at 3PM, the 15th and 16th showing especially muggy 80 F and 77 F figures, respectively, at daybreak. The 15th reached 93 F for the summer’s warmest temperature. Thunderstorms finally broke the spell in the early morning hours of the 17th and the rest of the month was considerably cooler and drier. Just several afternoons got warmer than 80 F. Pleasant to cool temperatures characterized almost all of August (mean temperature: 67 F), only a single afternoon warmer than the mid-80’s occurring all month (89 F on the 7th), just one higher than 80 F after the 15th. Rainfall was 2.49 inches on 12 days. The 30th was only 61 F at 3PM, the mercury dropping to 47 F by the following sunrise for the month’s coolest reading.

Record Daily Heat in October & November – Autumn was roughly seasonable in temperature overall with relatively heavy rains in September but infrequent falls in October and November. The latter two months each had Snelling era absolute maximum temperature marks set. September (mean temperature: 58 F) was generally cool and autumnal over the first half, milder over the second. Rainfall, uniformly distributed, fell on 12 days to 4.00 inches. The mercury hit 87 F on the 1st for month’s highest, but just two other afternoons got as warm as 70 F over the next seventeen, the season’s first frost visiting on the 8th. A “heavy” occurrence came on the 12th (temperature: 39 F at sunrise). The month’s warmest spell came late, the 20th-22nd recording 77 F, 80 F, and 78 F, respectively, the 30th also registering 78 F. A “smokey” atmosphere was noted for the 28th with an Aurora Borealis seen on the evening of the 29th. October (mean temperature: 47 F) brought changeable temperatures and only one day with measurable precipitation. Meteorological history was made on the 3rd as 91 F was reached at 3:20 PM, breaking 1839’s previous high mark by eight degrees F. Most other afternoons over the first ten days reached the 70’s, including 75 F on the 9th, but following 0.37 inches of snow & rain mixed on the 11th-12th, the season’s first hard freeze visited on the 14th with 21 F at sunrise. Day-to-day temperatures through month-end were quite variable, most afternoons in the 40’s and 50’s, mornings generally in the 20’s or 30’s. Another cold outbreak brought 14 F on the morning of the 26th, the mercury only 37 F at mid-afternoon, but readings began to swing back upward again over the month’s final days, 70 F recorded on the 30th, the temperature 57 F at the following sunrise. A “smokey” atmosphere was noted for each of the last four, remote lights from distant fires “in every direction” observed on Halloween night. November (mean temperature: 30 F) brought another monthly record high temperature. Total precipitation was 1.71 inches on 3 days. On the 2nd the mercury soared to 74 F, breaking 1825’s mark by 5 F, and like October’s record, a standard for the entire Snelling era. Marked change came over the next several days, the 6th and 7th bringing a sloppy mixture of “hail and snow with rain” that left 1.40 inches. Another inch of snow followed on the 9th, the next day below freezing throughout with ice starting to run in the Mississippi. The 16th recovered to 51 F, but 2 inches’ snow fell next day. Only a few of the month’s remaining afternoons got as warm as 40 F, temperatures subfreezing nearly all of the last week. On the 28th the mercury dipped to 9 F, the Mississippi freezing over this day. December (mean temperature: 16 F) had mostly moderate cold over the first half but a mix of arctic weather and thaws over the second. Melting temperatures were observed just twice over the first 16 days, with a 4-inch snowstorm coming on the 7th. The season’s initial arctic spell set in over the 24th to 26th, the mercury dipping to -19 F on the morning of the latter. Afternoon temperatures hovered around zero on each of the three afternoons. A strong surge of mild and damp air moved in to close the year, the mercury 38 F on the morning of the 29th, 44 F in the afternoon. New Year’s Eve Day was thawing all day with “dense fog at sunrise” and “mist through the day”.