The country's meteorologists consider the season to have officially started when the mercury tops 22 degrees Celsius (71 Fahrenheit) for five straight days, which it did from Thursday to Monday, the China Daily newspaper said.

It was the earliest occurrence since 1971, it said, quoting the Beijing Meteorological Station.

The temperature rose to 33.5 degrees Celsius (92 Fahrenheit) on Monday, the highest in the capital this year and hottest for that date since 1986.

Sunny weather expected in Shanghai could also mean the earliest summer in the commercial hub in 100 years, the paper quoted weather officials there as saying.

China Daily also said the average temperature across the country in April was 1 degree Celsius higher than normal, quoting a report by the National Meteorological Centre.

The early summer follows one of the warmest winters in decades and a sizzling 2006, China's hottest year since 1951, according to government figures.

The country's former top meteorologist said earlier this year that a rash of extreme weather last year including droughts and severe storms was likely due to higher temperatures caused by greenhouse gas-induced global warming.

Temperatures are expected to climb further in coming years, which could increase the risk of extreme weather events, including an accelerating retreat of glaciers in Tibet and other areas of China, meteorologists have warned.

China is expected to soon overtake the United States as the world's biggest emitter of carbon dioxide and other greenhouse gases, according to the International Energy Agency (IEA).

The government has called for a reduction in emissions, but has lowered its targets after missing previously set goals last year.

Meanwhile, China continues to build coal-fired power plants, which spew huge amounts of carbon dioxide, at a rate of more than one a week.

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