In recent years, average temperatures in the county seat of Moorhead have ranged from a low of 0 °F (−18 °C) in January to a high of 82 °F (28 °C) in July, although a record low of −48 °F (−44 °C) was recorded in January 1887 and a record high of 114 °F (46 °C) was recorded in July 1936. Average monthly precipitation ranged from 0.64 inches (16 mm) in February to 3.90 inches (99 mm) in June.
There were 18,670 households out of which 33.80% had children under the age of 18 living with them, 53.90% were married couples living together, 8.80% had a female householder with no husband present, and 33.90% were non-families. 26.10% of all households were made up of individuals and 10.60% had someone living alone who was 65 years of age or older. The average household size was 2.53 and the average family size was 3.07.
In the county the population was spread out with 25.00% under the age of 18, 17.10% from 18 to 24, 25.70% from 25 to 44, 19.30% from 45 to 64, and 12.90% who were 65 years of age or older. The median age was 32 years. For every 100 females there were 93.70 males. For every 100 females age 18 and over, there were 89.10 males.
The median income for a household in the county was $37,889, and the median income for a family was $49,192. Males had a median income of $34,176 versus $23,149 for females. The per capita income for the county was $17,557. About 7.40% of families and 13.20% of the population were below the poverty line, including 13.30% of those under age 18 and 7.50% of those age 65 or over.