Gunnedah police are urging residents and visitors attending the 2019 AgQuip Field Days to lock up their cars.
Sergeant Mark Benson said it was an "opportunistic" time for thieves, as there were more cars to try to break into.
"Local crooks look forward to it because there's more door handles to try," Sergeant Benson said.
"The site out there is locked up of a night and there's patrols with security guards out there, [but] everybody lock up their stuff anyway."
Sergeant Benson said overall the past few years hadn't been too bad.
"When I first got to town there was teenagers that would skulk around in the [AgQuip] car park trying door handles ... but generally it's pretty good," he said.
"We just want to reinforce that crooks don't have days off and it's their job to break into your stuff if it's not secured."
Hitting the road
Gunnedah residents and visitors to town are also urged to keep road closures and speed restrictions in mind during the AgQuip week.
New Street and View Street will be closed between 7am-11am and 3pm-6pm, dependent on traffic flows, on Tuesday, Wednesday and Thursday.
Blackjack Road's Oxley Highway intersection will close between 7am-7pm, dependent on traffic flows, on Tuesday, Wednesday and Thursday.
There may also be changed traffic conditions to Blackjack Road from the Oxley Highway and Quia Road.
Temporary lanes may be formed from the Oxley Highway to AgQuip gates 1 and 2 pending traffic flow.
From Quia Road to gate 1, it will remain a two-lane road.
Kamilaroi Highway and Oxley Highway will also have speed restrictions put in place.
Signage will show road users the speed limit.