Weir is a city in Williamson County, Texas, United States. The population was 591 at the 2000 census, and 637 in the 2005 census estimate.
As of the census of 2000, there were 591 people, 216 households, and 158 families residing in the city. The population density was 143.5/km (371.0/mi). There were 229 housing units at an average density of 55.6/km (143.7/mi). The racial makeup of the city was 90.36% White, 1.02% African American, 2.88% Native American, 4.06% from other races, and 1.69% from two or more races. Hispanic or Latino of any race were 16.92% of the population.
There were 216 households out of which 42.1% had children under the age of 18 living with them, 58.8% were married couples living together, 10.6% had a female householder with no husband present, and 26.4% were non-families. 21.3% of all households were made up of individuals and 5.6% had someone living alone who was 65 years of age or older. The average household size was 2.74 and the average family size was 3.19.
In the city the population was spread out with 31.1% under the age of 18, 7.6% from 18 to 24, 32.5% from 25 to 44, 20.3% from 45 to 64, and 8.5% who were 65 years of age or older. The median age was 32 years. For every 100 females there were 92.5 males. For every 100 females age 18 and over, there were 97.6 males.
The median income for a household in the city was $46,029, and the median income for a family was $47,813. Males had a median income of $32,216 versus $22,386 for females. The per capita income for the city was $19,361. About 3.6% of families and 5.2% of the population were below the poverty line, including 5.9% of those under age 18 and none of those age 65 or over.