South-east Queensland is mopping up after being battered by a line of intense thunderstorms that cut power to more than 27,000 homes and businesses.

Parts of Canberra have received more than the city's June average rainfall in less than two days with more rain on the way.

Gusty winds buffeted parts of Sydney late on Tuesday as a band of dry thunderstorms moved across parts of eastern NSW.

A high-pressure system "as big as Australia" will bring Melbourne's warmest patch of weather in more than five months, while most of the country is likely to go for a week with little rain.

Canberrans will face one of the worst fire danger days of the bushfire season on Tuesday as the temperature soars past 30 degrees amid dry, windy conditions.