According to the United States Census Bureau, the city has a total area of 42.5 square miles (109.9 km²), of which, 17.6 square miles (45.5 km²) of it is land and 24.9 square miles (64.5 km²) of it (58.63%) is water.
Wainwright has an Arctic climate with temperatures all the way from -56 to 80°F. There is little precipitation, mostly snow. The Chukchi Sea is unfrozen from mid-July through September.
There were 148 households out of which 50.0% had children under the age of 18 living with them, 50.7% were married couples living together, 16.2% had a female householder with no husband present, and 20.3% were non-families. 18.2% of all households were made up of individuals and 3.4% had someone living alone who was 65 years of age or older. The average household size was 3.69 and the average family size was 4.17.
In the city the population was spread out with 37.7% under the age of 18, 13.4% from 18 to 24, 27.8% from 25 to 44, 14.3% from 45 to 64, and 6.8% who were 65 years of age or older. The median age was 24 years. For every 100 females there were 114.1 males. For every 100 females age 18 and over, there were 117.9 males.
The median income for a household in the city was $54,722, and the median income for a family was $58,125. Males had a median income of $36,667 versus $40,313 for females. The per capita income for the city was $16,709. About 8.5% of families and 12.5% of the population were below the poverty line, including 18.4% of those under age 18 and 5.3% of those age 65 or over.