A cow doing what cows do best holds the key to one of Port Douglas State School's biggest fundraisers of the year to be held next Saturday, 8 September.

And one lucky punter will be $5000 better off as Cow Pat Lotto takes centre stage.

Never heard of Cow Pat Lotto? Here's how it will play out.

A grid of 100 x 1 metre numbered squares is to be marked on the school oval, and punters buy a square for $100.

Enter the bovine.

The cow wanders around the grid, munching on grass, wondering what the fuss is all about. When nature calls, whatever number cops the brunt of the cow pat will be declared the winner and mooove the number's owner to tears.

If Cow Pat Lotto isn't your thing, there'll live entertainment, cake stalls, BBQ and bar, and a good old fashioned Car Boot Sale.

For more information on the Family Fun Day, or to book a space for your car boot goodies, contact Jenni Walker at walkerlj@telstra.com.