Allen is a city in Collin County, Texas, United States, a wealthy northern suburb of Dallas. As of the 2010 census the city had a total population of 84,246.
According to the City of Allen, the city has a total area of 27.1 square miles (70.2 km²). None of the area is covered with water except the small ponds scattered throughout the city.
Allen is considered to be part of the humid continental region, meaning it experiences mild to very cold winter with temperatures in winter ranging from 21 to 43 °F (-6 to 6 °C) in daytime and 8 to 30 °F (-13 to -1 °C) at nighttime. In spring the city has severe thunderstorms and mild warm days; temperatures range from 50 to 70 °F (10 to 21 °C) in daytime and 37 to 57 °F (3 to 14 °C) at night. In summer the city experiences very hot days ranging from 90 to 100 °F (32 to 38 °C). In the autumn the daytime temperatures vary from about 85 to 40 °F (29 to 4 °C).