A slight hint of the future, as in The public unrest is a straw in the wind indicating future problems for the regime. This expression alludes to a straw showing in what direction the wind blows, an observation also behind the idiom straw vote.

A small sign that hints of something that is about to happen: “It is difficult to tell whether the new regime will relax censorship, although a recent remark by the minister of culture may be a straw in the wind.”