Montgomery County prosecutors Warren Diepraam says authorities see a 20 to 30 percent increase in DWI numbers during Renfest.
The event takes place through November but Diepraam expects lots of activity this weekend in particular.
"It's kind of a confluence of the Renaissance Festival and Halloween, which also sees a big increase in DWI driving and crashes."
Renfest happens near Magnolia, and Diepraam says police will focus much of their efforts on State Highway 249. He says they've gotten good cooperation from Renfest promoters.
"It's family event out there, they want people to have fun. They want people to come back, and if the festival gets a reputation as a drunk fest, or having too many DWI crashes, that's not going to reflect well on the Renaissance Festival."
Police are also conducting a "No Refusal" effort. It starts at 9:00 Saturday evening and runs until 4:00 Sunday morning.
During a No Refusal period, police can get immediate search warrants for a blood sample if someone suspected of driving drunk refuses to take a breath test.
Diepraam says local police who have been trained as paramedics have been authorized to take those samples. They can draw blood either at a mobile unit or a local jails.