Minnesota (Fort Snelling) weather for the year 1845

Much Warmer

Thermal patterns underwent a marked shift during 1845 at Fort Snelling, with generally above normal temperatures throughout the whole year. Annual mean temperature (46 F) was 4 F higher than 1844, January to June the warmest such monthly interval in twelve years. The only noteworthy extended periods of unseasonable cold came during November and December. Total precipitation was 25 1/3 inches, early June having some especially frequent and heavy rains that produced what must have been a healthy “June-rise” of the rivers.

Very Mild Winter, Another Early Spring Breakup – Infrequent snows and almost uninterrupted mild temperatures featured the new year’s side of the ’44-’45 winter. January (mean temperature: 19 F) was mostly sunny with light winds. Afternoons consistently reached the 20’s or 30’s, nights generally in the teens or single figures. The only subzero sunrise temperature was -12 F on the 31st. Snowfall was about 5 inches, nearly all of it coming from a four-inch storm during the third week. Subzero cold opened February (mean temperature for the month: 25 F), minus 4 recorded on the 1st. This, however, would be the winter’s last subzero day. Afternoon temperatures through the second week continued mostly in the teens and twenties, but following a 6 1/2 inch snowstorm on the 13th-14th, another abrupt mid-February mild shift set in. Afternoon observations in the mid-40’s were routine from this point through the close, the six-day period the 18th-24th thawing almost continuously. Conditions on the 19th were April-like, daily temperature range from 40 F to 52 F, hail and .70 inches of rain falling in the evening. Similarly unseasonable temperatures prevailed on the 24th, the daily readings ranging from 35 F to 49 F. An Aurora Borealis was also viewed in the evening. March (mean temperature: 34 F) was likewise mild, and until the last days, very dry. Just .22 inches’ precipitation fell over the first 27 days. Roller-coaster temperature gyrations, prairie fires, and heavy rains featured the last two weeks. Following 57 F on the afternoon of the 16th, warmest of the month thus far, a late arctic pulse brought 3 F readings on both the 18th and 19th, afternoon temperatures on each confined to the low 20’s. Strong northwesterly winds on the evening of the former created some of the bitterest windchills since last November, the 9PM reading just 10 F coupled with force 5 winds (35 miles per hour). Temperatures rebounded to the mid-40’s again over the next several days, ice seen running in the Mississippi on the 23rd. Then on the 26th, a sudden summery surge sent the mercury to 79 F, breaking 1838’s record for March heat. Cooler but still unseasonably mild temperatures, in the low 60’s, followed again next day (the 27th). On the 28th, another warm surge drove the temperature to 80 F, breaking the record again, and a spectacular late afternoon/early evening lookout scene prompted special notes from Surgeon George Turner: “[At] 5 1/2 PM Thermometer 80, Wind S.[at Force] 5, fires raging furiously SE & S. Thunder & Lightning, Barometer 28.780 at 6 1/4 PM…” Following overnight passage of the storm and its trailing cold front, temperatures only recovered to the 50’s next afternoon (the 29th). But yet another warm wave pushed the mercury to 72 F on the 30th, preceded by .46 inches’ of morning showers. Much colder air invaded the area overnight, its approach setting off powerful thunderstorms which drenched the Post with 1.92 inches’ rain and hail. The 31st was decidedly wintry, afternoon temperatures only in the mid-20’s with strong northwesterly winds. Snow, evidently not measurable, was also seen. This being the season’s last, total accumulation for the ’44-’45 season finished at a modest 25 inches, approximately.

Mild/Dry Spring – April (mean temperature: 47 F), relatively mild overall, saw the spring advance stall over the first week or so. Especially chilly temperatures comprised the 4th through 8th, readings no higher than 40 F with occasionally strong northwesterly winds. The opening of Lake Pepin on the 6th was probably aided as a result. The 7th was almost January-like with 15 F at sunrise, accompanied by force 4 northerlies, the mercury still only 22 F at 3PM. A great warming then followed, 65 F reached on the 9th and 82 F on the 12th. Temperatures over the last half resumed March’s large afternoon-to-afternoon variability pattern, fluctuating from the mid-40’s to upper 70’s and back again over several-day stretches. Some 3.15 inches’ precipitation also came over the last seventeen days, none having fallen over the first thirteen. In marked contrast with the last three years, May (mean temperature: 60 F) was warm, sunny and dry. Only one appreciable rainfall occurred all month, an inch over the 20th-21st. Total for the month was a modest 1.51 inches, average 3PM clearness of the sky 7.6. Following a few cool days over the first week, diurnal ranges typically in the upper 30’s to 50’s, premature summer-like warmth and humidity set in for five days beginning on the 8th. Mornings were generally in the 60’s, four of the afternoons climbing to between 82 F and 86 F. The last part was cooler, eight of the last twelve afternoons confined to the 60’s or lower, a slight frost observed on the 29th.

Very Wet Early June, Warm July – June (mean temperature: 68 F) gave a good demonstration of the local natural tendency for frequent and heavy rains at this time of year. Some 6.37 inches fell through the 15th, the Mississippi and St. Peter’s rising 4 feet by the 7th, remaining “at a stand” through at least the 16th. Few afternoons got as warm as 80 F over the first three weeks, nearly half in the 60’s. Some light frost was even reported on the 17th. Temperatures began to warm over the last nine days, each in the 80’s or warmer, 91 F read on the 26th. Accompanying the warmer temperatures, just 0.43 inches’ precipitation was measured over the last two weeks. July (mean temperature: 75 F) was the warmest calendar month in six years, 2.56 inches’ rainfall recorded on sixteen days. A week-long hot spell prevailed over the 9th to 15th, afternoon temperatures ranging from 89 F to 94 F, evenings notably sultry, exemplified by sunrise temperatures of 76 F, 79 F, and 77 F starting with the 10th. The heat then subsided somewhat, just several of the remaining afternoons approaching or reaching 90 F. Nights remained warm, only a few cooler than the mid-60’s.

Pleasant August/September – August (mean temperature: 70 F) brought a cooling, most afternoons in the 70’s with no 90’s. A few scattered warm and humid days with diurnal temperature ranges between the upper 60’s to the mid-to-upper 80’s were experienced, but no hot spells of any note occurred. Rainfall was 3.28 inches on nine falls. September (mean temperature: 61 F) was the warmest in seven years with many sunny days. Total rain was 2.21 inches on 8 days. The 6th was the season’s last warm, humid day, the diurnal range 65 F to 82 F, but cooler weather followed, the 10th’s spread 47 F to 69 F with geese seen “passing south”. Most afternoons thereafter were in the 60’s to low 70’s, daily range on the 21st 35 F to 58 F with the first frost of the season noted. Thunderstorms on the 28th dropped 1.16 inches’ rain.

Dry Fall/Early Winter, Premature Arctic Cold – Fall and early winter were quite dry with plenty of Indian Summer weather, but also, for the second successive year, unseasonably early and bitter November cold. October (mean temperature: 46 F), brought fluctuating temperature spells and prairie fires. Just five days had rain, totaling .66 inch, the 14th-28th precipitation-free. Smoky atmospheric conditions and fires were present on almost each day past mid-month. Temperatures over the first nine ranged generally from the 30’s or 40’s in the mornings to the 50’s or 60’s in the afternoons. A couple of mornings with hoarfrost were also noted. A six-day spell of cool and crisp weather next ensued, afternoons in the 30’s and 40’s, some snow and rain mixed coming on the 13th. The sunrise mercury reading was 18 F on the 15th, the month’s minimum. On the 18th, the temperature hit 72 F, but the next four afternoons were only in the 40’s. The last week turned out to be the month’s mildest, daily temperatures ranging mostly from the low 50’s in the mornings to the low 60’s or low 70’s for the afternoons. November (mean temperature: 30 F) was one of contrasts, with lingering mildness past mid-month but a precipitous descent to bitter arctic cold over the last few days. Precipitation remained light, just .36 inches received on three days. Conditions over the first half were mild and pleasant for the season, mostly partly cloudy with daily temperature ranges from the 20’s and 30’s to the high 40’s and 50’s. The 13th reached 60 F and the 15th 68 F. Following the first precipitation of the month, .31 inches’ rain over the 16th-17th, a gradual but steep thermal decline began. No thawing temperature were registered after the 20th, the last four days predominated by arctic cold and bitter northwesterly winds. Warmest reading over the 27th-30th was just 5 F, overnight temperatures falling to between –7 F and -12 F. The 27th was one of the rawest November mornings in Post experience, minus 12 F observed at sunrise combined with force 4 northwesterlies (25 miles per hour). December (mean temperature: 14 F), coldest in seven years, had some curiously oscillating cold and mild spells. Precipitation was very light, about an inch of snow. Late November’s closing cold continued over the first ten days with half the mornings subzero, two as low as -11 F and -12 F. On the 12th, a mild term suddenly set in for six days, afternoon readings reaching to between 29 F and 38 F. This was followed by another cold spell persisting for nine more, most mornings ranging from -12 F to single figures above zero. The 18th brought some more dangerous windchills, -8 F temperatures observed at both sunrise and 3PM, winds noted from the west-northwest at force 5 (35 miles per hour) and force 4 (25 miles per hour), respectively. Temperatures began to moderate again after Christmas, and preview of a historically warm January now to come, 46 F, 44 F, and 44 F readings were registered on the closing three afternoons of the year, respectively.