It's not over until the snowman melts

A politically correct version of "It ain't over till the fat lady sings". It means that one should not presume to know the outcome of an season or event which is still in progress. A phrase is used when a situation or season is (or appears to be) nearing its conclusion. It cautions against assuming that the current state of an season or event is irreversible and clearly determines how or when the event will end. The phrase is most commonly used in association with the end of the winter season pending the last frost.

Don't plant your crops to early as "It's not over until the snowman melts"