Joal Pippard, a meteorologist with weatherzone, says the forecast does not bode well for Anzac Day services.

"The coastal trough is forming and is sitting just off the coast," he said.

"This is not particularly unusual for this time of the year. Ocean temperatures are higher at this time of the year - we refer to this as the maritime summer."

Mr Pippard said the Bureau of Meteorology on Monday issued a rainfall warning for the coast.

"These storms could bring more than 20 millimetres of rain and in a short space of time. There will be widespread falls, especially right on the coastline.

"While the modelling is a bit uncertain at this point, there is a suggestion of a low pressure system forming within this trough.

"We are pretty much guaranteed showers and storms through Tuesday and Wednesday. The low may also bring strong winds and swell."

The swell on Wednesday is forecast to one metre but could be as high as three.

Winds could also vary from 40 to 60 kilometres per hour and with the expected low that could also climb above 80kmh.

Showers are expected to persist - along with sunny patches - through to Monday.

"Southerly winds will pick up from Wednesday, driving moist onshore winds onto the coastline," he added.