Melburnians know where their rainy weather comes from, and it's usually from one of two directions.

It's either warm, wet stuff out of the north and northwest, or it's freezing cold bands of showers that skid their way across the bay from the west, southwest or south before spraying the city and suburbs with a mix of rain and/or hail.

In both scenarios, Melbourne's rain tends to come in bursts rather than sticking around all day. But today, all the rules are broken. Firstly, Melbourne is already several hours into a prolonged downpour of persistent, steady rain. And secondly, the wet stuff is coming from the east.

Indeed right now, you have to say it's a Sydney-type system, as Sydney often gets prolonged rain out of the east with a blob-style image on the radar that seems to hover over the city and surrounds, in no hurry to park its large green backside anywhere else anytime soon.

Yes, an image just like the Melbourne radar at 3 pm Thursday:

So what's going on?

Glad you (we) asked!

As you've no doubt gleaned if you've been hanging around our site or app lately (or indeed if you live in the eastern half of Australia and have looked out the window), there's a lot of weather around this week.

Today's weather – which is affecting not just Melbourne but virtually all of Victoria and especially the eastern half of the state – is being caused by a surface low moving through Bass Strait from east to west.

As mentioned, this is a reasonably unusual set-up, but the easterly flow makes sense if you look at that low pessure system in Bass Strait and remember that winds move clockwise around a low.

There's plenty of moist air being funnelled into Victoria today, and while the rain is for now pretty steady stuff in most areas, there is absolutely the potential for severe storms to break out, both today and tomorrow. These storms could be isolated or could be embedded as part of a larger rainband.

Check out WZ meteorologist Ben Domensino's story on where storms are likely tomorrow on the fourth day of this major spring outbreak of rain and storms in eastern Australia. And remember to check warnings for your area, as flash flooding is always a possibility with any storm activity. Our warnings page is here.