Thursday, July 02, 2009

Weather Early Observations II

The precipitation climate of 1807-8 was quite different, however, with more frequent occurrence of snow and rain during November through March. Snowfall totals were at least 10 and 20 inches, respectively, for the months of November and December, considerably higher than the modern averages taken from Hallock - 5.4 inches for November and 5.1 inches for December - and Pembina - 5.3 inches for November and 5.4 inches for December. In this context the Red River probably flowed at a higher level during Henry's time there, lacking as it did the agricultural drainage and reservoirs or holding ponds that characterize the valley today.

Some of Henry's remarks and climate summaries from 1807-8 are worth noting:

Following early September warmth, with temperatures as high as 89F, Monday the seventh brought a frost to the valley that ended the growing season for cucumbers and melons. These temperatures helped trigger a change in leaf color on most of the trees. Thunderstorms, with large hail and strong winds, occurred at mid-month, followed by 2 inches of snowfall near where Two Rivers joins the Red River of the North, just west of present-day Hallock, a number of hard freezes, with temperatures dipping into the twenties, were noted in the second half of the month.

Corn and potatoes were harvested the first few days of October. A luminescent star with a long tail was noted in the western sky; this feature (perhaps a comet) lasted until mid-November. Numerous prairie fires occurred during the month, some producing enough smoke to drastically reduce visibility. Fires were a common occurrence on the prairie landscape throughout the nineteenth century: the dry native grasses provided excellent fuels easily ignited by cloud-to-ground lightning strikes.

November brought frequent snows and cold. Snowfall occurred on 15 days, probably totaling more than 10 inches for the month. The Red River was frozen over by the twelfth and could accommodate foot and sled traffic by mid-month as the temperature fell to -1F on November 14.

Very cold temperatures and abundant snow continued in December. The month's snowfall total exceeded 20 inches. Temperatures fell below zero degrees Fahrenheit on seven days, reaching a low of -17F on the seventeenth. In fact, on four days the temperature never rose above zero. Combined with very strong winds, these low temperatures produced some dangerous wind-chill values, but of course this was long before the concept of "wind chill" had ever been proposed. Nevertheless, one could infer that layered clothing under a buffalo robe was the rule.

January's cold temperatures produced halos around the sun and moon on several occasions. Fifteen days registered below-zero temperatures. Unlike the late-twentieth-century climate of the Red River valley, which showed a high frequency of January thaws, there was no thaw period - or even a single day above freezing - in January 1808. There were 11 days with snowfall, and a good deal of blowing and drifting.

February 2 (Groundhog Day) brought the first thaw, as the temperature reached an afternoon nigh of 36F. But this relative warmth was only a tease, as the rest of the month brought 15 more days of below-zero temperatures, some with presumably dangerous wind-chill conditions due to high winds. February ended on a warming trend, reaching a high of 42F on the twenty-eighth and melting quite a bit of snow cover.

Early March saw the warm spell continue, with three consecutive days in the forties. Henry observed migrating swans the first week of the month, followed by buzzards. By March 13, water began to flow over the top of the ice in the Red River. Six inches of fresh snow was noted at mid-month, then alternating freeze-thaw periods. Four nights recorded below-zero readings, the coldest, -7F, coming on the morning of the twelfth. The month's high temperature, 52F, was recorded on the twenty-sixth.

April 2 brought a snowstorm, but it was followed by a pronounced thawing period. Several days saw temperatures in the forties and fifties, and on the eighth the ice broke up on the Red River and started to flow north. Henry observed abundant migrating waterfowl, often resting along the river's banks. He caught the season's first fish on April 7. With the prolonged warm spell and absence of significant precipitation, the ice break-up occurred in relatively short order. The daytime temperature hit 65F on the twelfth, and the river level began to drop two days later, falling 2 feet in a 24-hour period. The last week of April, Henry and his men enjoyed great success as they fished for sturgeon. April 27-29 saw summer like temperatures - highs in the mid-to-upper eighties (89F on the twenty-ninth) - and a substantial rainstorm ended the month.

May brought wide swings in temperature and even a snowstorm on the third, the last of the season. Alternating high-low temperatures and very strong winds indicated numerous cold fronts passing through. Temperatures ranged from 28F on the fourth to 86F on the eighteenth. Sturgeon fishing remained very good: Henry noted taking up to one hundred fish per day out of the Red River.

Henry's climate records for 1807-8 end on June 1, a sultry day with a high of 92F and a low of only 70F. From his journal entries and daily weather observations - one of the few such documents of the region prior to the establishment of Fort Snelling in 1819 - we have a picture of the harshness, beauty, and serenity of the Red River Valley's landscape and climate.

From Minnesota Weather Almanac, by Mark W. Seeley (Published by Minnesota Historical Society © 2006)