You don't need a weatherman to know which way the wind blows

...but they do come in handy when it comes to predicting rain. And it seems a hard rain's gonna fall next week. This will at least fill up my cisterns, which is the fancy-shmancy word I use for the feed barrels that I collect rainwater in (above).
Timing when to clean the cisterns is a kind of art. I'm not going to exaggerate how complicated this is, but it's a good idea to clean and scrub them just before it rains. That way, you're not going to get stuck with clean, but empty barrels.
Or dirty, full ones.