In winter, the average temperature at Ottertail and Fergus Falls is 11 degrees F. The average daily minimum temperature is 0 degrees at Ottertail and 1 degree at Fergus Falls. The lowest temperature on record at Ottertail, which occurred on February 3, 1982, is -41 degrees. The lowest temperature on record at Fergus Falls, which occurred on February 5, 1982, is -40 degrees.
In summer, the average temperature is 69 degrees at Ottertail and 68 degrees at Fergus Falls. The average daily maximum temperature is 80 degrees at both recording stations. The highest temperature at Ottertail, which occurred on July 27, 1988, is 102 degrees. The highest temperature at Fergus Falls, which occurred on August 16, 1988, also is 102 degrees.
Growing degree days are equivalent to “heat units.” During the month, growing degree days accumulate by the amount that the average temperature each day exceeds a base temperature (40 degrees F). The normal monthly accumulation is used to schedule single or successive plantings of a crop between the last freeze in spring and the first freeze in fall.
The total annual precipitation at Ottertail is 26.56 inches. Of this, 19.45 inches, or about 73 percent, usually falls in April through September. The total annual precipitation at Fergus Falls is 23.25 inches. Of this, 17.46 inches, or 75 percent, usually falls in April through September. The growing season for most crops falls within this period. The heaviest 1-day rainfall during the period of record was 4.4 inches at Ottertail on June 19, 1979, and 4.3 inches at Fergus Falls on August 7, 1992. Thunderstorms occur on about 32 days each year, and most occur in July.
The average seasonal snowfall is 49.9 inches at Ottertail and 40.3 inches at Fergus Falls. The greatest snow depth at any one time during the period of record was 34 inches at Ottertail and 27 inches at Fergus Falls. The heaviest 1-day snowfall on record was 14 inches at Ottertail and 12 inches at Fergus Falls.
The average relative humidity in mid-afternoon is about 62%. Humidity is higher at night, and the average at dawn is about 81%.
The prevailing wind is from the south-southeast. Average wind speed is highest, 14 miles per hour, in April. Additional information about the Nation's natural resources is available on the Natural Resources Conservation Service website.