Queen's Birthday Weekend drivers beware: Monday's gypsy day could cause you a few headaches.

Gypsy day usually occurs in the middle of the year as farms change hands between owners or farm workers in time for the new dairy season.

Drivers are being urged to slow down on country roads, as thousands of cattle take to the roads.

Federated Farmers mid-Canterbury president Willy Leferink maintains the recent drought means some farmers have already moved or sold stock.

"A lot of cows have been shifted already but there's still a lot of traffic to go on so just be careful," he said. "If you see flashing lights and high visibility vests then it will be likely there are some cows on the road."

"Be careful on any roads. [There'll be] cows left right and centre on the road. Be seen, make sure there is plenty of people around the herd, drive slow, and everybody will be fine.