Cool air in the upper atmosphere will drift over WA during the end of the weekend, enhancing a surface trough that is already firing storms through the interior.

Much of the storm activity is expected to concentrate in two main areas. Through the western interior, with a second patch clipping the west coast.

Storms are expected to fire along the coast from mid to late afternoon (Sunday) and could deliver totals upwards of 40mm. Computer models currently put the main storm zone on the west coast sitting north of Perth, towards Geraldton.

Overnight and into Monday though, the trough will extend southwards, sending storms down to the southwest. Again, the heaviest falls are expected north of and inland of Perth.

The parched city is staggering towards its wetter months and forecasts suggest as much as 10 to 15mm could fall over the next few days. If it does, it would be the best rain since November 2009.

So far this month Perth has recorded no rainfall.

A meagre 0.2mm was the summer accumulation.

The mean for March is 21mm.