Masterton mayor Lyn Patterson judged the competition.
"It's great to see women coming together, having a bit of fun, and doing something for the community," Mrs Patterson said.
"They have a good, proud history and a good, proud future."
Jean Paget received first prize for her cap, which she had transformed into a rooster.
"I made it in about a week," she said.
"I glued and put it together with feathers that had moulted from my chickens."
Second prize went to Carol Manson with a hat that displayed mini windmills on a patch of green felt.
"Her husband put it together," said past women's institute president Ann Jackson.
"He didn't want to have anything to do with flowers so he made that.
"It's great, isn't it?"
Third prize went to the smallest hat of all; one perched on the dog of one of the members.
Members had been told to bring "wheels" of different varieties to promote Riding High with Women's Institute and were encouraged to show their creative side.
They paraded their hats along the edge of the lake on a variety of wheels.
Mrs Jackson took part in the parade of hats on a scooter.
"You've got to be able to laugh at yourself," she said.
"You might look a bit daft, but it's fun."
Before the picnic, the day started with a morning tea at the Wairarapa Community Centre, to show the institute's support and to keep up to date with the community.
Altogether, a total of 13 branches of the women's institute operate throughout the Wairarapa and they boast more than 190 members among them.
