The appearance of hastily made signs advertising cheaply made Chinese umbrellas (often spelt incorrectly and sporting a redundant apostrophe) is an indication that the weather channel predicted fine conditions and it's been pissing down cats and dogs since lunchtime.
The sight of big blokes dressed in Santa suits is a sign that Xmas is on the way. But it also may indicate the first few weeks of October.
The completion of renovations to a hotel beer garden will often indicate the impending arrival of subartic winds or in some cases, the likelihood of a freak fire that will gut the entire building.
An influx of international rock bands who are prepared to do concerts in Cairns is one way to tell it's winter in the northern hemisphere.
The appearance of current affairs reporters with hairy chests in open-necked shirts hoping to bust people breaching water restrictions in your neighbourhood indicates the area is in drought. Or it could just mean there's a poor toothless family next door abusing animals.