More than 40,000 properties were left without power in southern Western Australia after damaging winds and heavy rainfall battered the coast.

Yachts were smashed in the powerful storm front, snapped off their moorings off Rockingham’s foreshore.

Tides were a metre higher than predicted.

“I could get really upset by it but there’s no point,” boaty Scott Davenport told 9NEWS.

“It is what it is unfortunately.”

State Emergency Service crews responded to almost 100 calls for help in 24 hours in Broadwater near Busselton, mainly to deal with flooding from the heavy rain.

Weatherzone said parts of Gascoyne District just had their wettest June day on record.

The slow-moving low pressure trough caused persistent and heavy rain over the western Gascoyne during Monday night, delivering widespread falls of 20-40mm.

Some areas along the coast received close to 100mm, which is double the entire monthly average for this time of year in this part of Western Australia.

Whie this is typically the wettest month of the year in the west Gascoyne, last night's deluge was unprecedented for some places during June.

Denham's 98mm of rain during the 24 hours to 9am on Tuesday was its heaviest daily rainfall total on record during June. Data for this site is available back to the early 1900's. This was also more rain than Denham had received during the last 15 months combined.

Nearby, Shark Bay's 96mm was its heaviest June daily rainfall total in 17 years of records and the heaviest for any month in three years. Carnarvon (32mm) also received its heaviest rain since 2015.

This rain-bearing trough will move slowly north and east in the coming days, allowing similarly heavy - potentially record-breaking - rainfall to spread across the Pilbara between now and Thursday.

Further south, a cold front crossing the state's South West Land Division on Tuesday is causing damaging winds, heavy showers and abnormally high tides.

Powerful northerly winds ahead of the approaching front produced gusts of 109km/h at Busselton Jetty and Rottnest Island, and 94km/h at Albany Airport early on Tuesday morning.

While Perth had only registered about 10mm from this system as of 2pm on Tuesday, Busselton managed to collect 24mm in just one hour during the morning.

Wind and rain will ease across the state's southwest this afternoon and tonight in the wake of the front, although another, weaker front will cause further showers and thunderstorms on Wednesday.

With Weatherzone

© AAP 2018