He urged drivers to show patience and courtesy if they encountered stock on the road during that time.
"People need to be aware that these animals are going to be out and about and you never know when you are going to meet them on the road."
In some parts of the country, stock were not allowed on the road, Mr Sexton said, instead having to be moved by truck or through underpasses.
He expected that would be introduced in Wairarapa in the future.
Most herds today were four or five times the size they were 20 years ago, he said, and the number of cars on the road had also risen dramatically.
"Both of those make a big difference," Mr Sexton said.
A spokesman for Masterton District Council said he did not expect any problems with cows on the roads over the next few weeks.
He said the two biggest dairy farms in the council's catchment were in the process of installing additional underpasses to keep stock off the roads.
Federated Farmers has reminded farmers to stand their stock for at least four hours before moving them, to help reduce the amount of effluent they produce while in transit.