On hot days like today, wherever you go in the city, there are big puddles of water on the footpaths, often running down into the gutters. Some of these puddles can be extremely slippery too, depending on the surface they are found.
The smart people are on the lookout for this sort of thing, just as they are for stray dog poo that lies along the footpaths. Apart from being slippery, or getting wet feet, there is the occasional heavy drop from the Air-conditioner above that has the very same feeling as being pooed on by a bird. A great big wet patch on your nice clothes does not look so great either.
So the best policy is to watch the air-conditioning drops.