More than 70,000 Perth homes are still without power after a severe thunderstorm caused up to 100 million Australian dollars (91 million U.S. dollars) damage in the West Australian capital.

State Premier Colin Barnett on Tuesday declared the city an insurance catastrophe as residents and authorities spent the day clearing fallen trees, fixing broken windows and assessing damage to homes and cars.

A narrow band of intense storm cells hit the northern suburb of Ocean Reef on Monday and moved south, down the city's 20km wide coastal strip, bringing with it an unusual trifecta of damaging winds, large hail stones and heavy rainfall.

Engineering assessments were being conducted on affected buildings across the city, including the Adelphi Apartments at the foot of Kings Park where a torrent of mud slid down a hill and smashed through ground floor windows. Residents were evacuated to the nearby Perth Convention Center.

Leaking ceiling and electrical hazards caused 14 schools across Perth to close. Most are likely to remain shut tomorrow.