overselling the weather

We haven’t had any rain for over seven weeks, and the garden is really suffering.  So we are constantly checking the forecast to see when this drought might end.  Here’s what my BBC Weather app says for next Wednesday:

Yay ! Rain at last!

So, we can look forward to the drought breaking on Wednesday, then?  Great!  When will it start to rain?  Let’s look at the hour-by-hour breakdown:

Umm

So, it’s going to rain for less than an hour?  How does that make the whole day summary be “light rain showers” and the background a dull grey?

And actually, there’s a mere 12% chance it will rain then.

Yet there’s a 17% chance of rain at 4pm, but no raindrop on that hour’s icon.

What do these symbols and percentages even mean?