The reason comes down to Houston’s guidelines, which are among the most stringent of Texas’ metropolitan areas, according to a review by the Houston Chronicle.

Houston opens its warming centers when the weather hits 24 degrees for two hours or more, or when there’s 15-degree windchill for two hours or more, a spokesperson for the city’s Office of Emergency Management said.

Meanwhile, most of the state’s major cities open their shelters at a threshold that’s several degrees warmer, when temperatures drop to around freezing.