Travis County is again under a burn ban.

During its Nov. 13 meeting, the Travis County Commissioners Court approved banning outdoor burning in unincorporated areas of the county.

The ban is set to expire Dec. 12 unless it is extended, said Lisa Block, Travis County Emergency Services spokeswoman.

"November and December are typically dry months for us, meaning low humidity," she said. "We haven't received rain in quite a while, so the ground is dry. Also, fall and winter grasses add fuel to potential fires."

The county measures moisture using the Keetch-Bryam Drought Index, in which zero represents saturation and 800 represents a complete lack of moisture.

Block said that on Nov. 13, the county average was 492 and the highest measurement was 577.

"There starts to be a stronger potential for fires as you approach 500 [on the index]," she said.