Outdoor Burning
Outdoor Burning Rules Are Narrow in Unincorporated Collin County
Outdoor burning in Collin County is tighter than many rural landowners expect. No county office, not even the Fire Marshal, can hand you permission to burn. Only TCEQ decides whether a particular burn fits one of the legal outdoor-burning exceptions, and the county simply defers to those state rules.
Burn bans are a separate switch on top of that. The county watches the Keetch-Byram Drought Index and can issue a ban for unincorporated Collin County when conditions are dry and no rain is coming. Once a ban is in effect, even an otherwise-legal burn is off the table until it lifts.
So before you light a brush pile outside the city limits, two things have to line up: the burn has to meet a TCEQ exception, and there can't be an active county ban that day. If a city, HOA, or fire district covers your address with stricter rules, those win too.
Source to confirm: Collin County Fire Marshal - Outdoor Burning