Severe thunderstorms capable of producing damaging winds, heavy rainfall and large hailstones will loom as a feature over Perth and WA's south-west for much of this week, as the state's north braces for another cyclone.

Key points: Perth's long, hot summer will be broken by storms this week

Perth's long, hot summer will be broken by storms this week Forecasters are warning they could be strong but highly localised

Forecasters are warning they could be strong but highly localised It comes as Cyclone Esther heads towards northern WA from the NT

The muggy, stormy weather over south-western parts of the state is the result of a slow-moving trough of low pressure near the west coast interacting with a moist and unstable airmass.

"Some of those thunderstorms have the potential to be severe in nature, which means they could produce wind gusts of 90 kilometres an hour or more, hail of 2 centimetres or more in diameter and rainfall that could lead to flash flooding," Bureau of Meteorology (BOM) spokesman Neil Bennett said.

"They don't happen very often in Perth, it has to be said, they're usually further to the east, but sometimes if the conditions are right we can see them in the Perth area."

Muggy weather will be a feature across Perth this week. ( ABC News: Jon Sambell )

Although rain is forecast for much of the week, the hit-and-miss nature of thunderstorms means that some areas will miss out entirely while others will be hit hard.

"It's very tricky to forecast for thunderstorms because they are quite isolated in their nature," Mr Bennett said.

"You only have to be 5 or 10 kilometres away from the centre and you get nothing at all, but if you're right underneath it then you get the absolute full fury of one.

"For a short period of time the rain can be very intense and very heavy, you could get the hail — that doesn't always happen, but we have to warn for the risk of it."

Cyclone risk facing WA's north

Australia's fourth cyclone of the season, Esther, made landfall in the Gulf of Carpentaria near the Northern Territory and Queensland border as a category one system on Monday afternoon.

It is expected to weaken to a tropical low before heading west, with the Kimberley in its sights.

"As it moves into the Kimberley region on Thursday in particular, we could see some heavy rainfall out of the remnants of Esther, and then it will re-intensify [into a cyclone] probably on Saturday just to the north of Broome," Mr Bennett said.

"There is a very strong risk now of a tropical cyclone in the Kimberley on Saturday and we will be monitoring that closely."

A coastal crossing in the Kimberley or Pilbara cannot be ruled out, but due to the erratic behaviour of cyclones, it is too early to predict its path beyond Saturday.

"There are some suggestions it will continue on the westward track and that brings the Kimberley and Pilbara coasts into play, but at the moment we don't have a very strong indication as to what's going to happen" Mr Bennett said.

Meanwhile, Australia's fifth cyclone of the season, Ferdinand, developed off the northern WA coast — about 700 kilometres north of Port Hedland — on Monday morning.

But Ferdinand is expected to stay offshore, well away from WA.

"It's currently a category one system and it's not expected to have any impact on the mainland," Mr Bennett said.

"It is expected to intensify though so by tomorrow it could be a severe tropical cyclone category three, but again, it's far enough to the north to not have any impact in terms of wind or rain."