Judy Liu has not had much sleep this past week but is too embarrassed to tell her friends the reason.

The bolts of lightning and thunder had made her hide under a quilt and her dog under the bed.

For several days the capital's sky has darkened much earlier than usual to be followed by lightning, thunder and heavy rain. Workers were trapped in offices, dinner plans cancelled, and traffic disrupted due to flooding.

More than 20,000 passengers were stranded at Beijing's Capital International Airport on Tuesday and Wednesday due to cancellation of flights.

Within half an hour more than 80 bolts of lightning zigzagged across Beijing's sky on Tuesday evening.

Meteorologists said that a single bolt of lightning is hotter than the sun, and in the time it takes to blink, lightning can strike the ground five times.

Other parts of the country also experienced the unusual weather.

On July 17, in the mountainous region of Chongqing Municipality, more than 41,672 incidents of thunder were recorded in a 10-hour period, the local meteorological bureau reported.

Wuhan in Hubei Province recorded 937 bolts of lightning on July 26, and 5,774 for the whole province.

In Shanghai, there were 11,195 incidents of thunder within a 48-hour period starting on July 9. Nanjing in Jiangsu Province witnessed 200 streaks of lightning within 30 minutes on July 10.

The Shanghai-based Morning News, quoting a meteorological expert, said the adverse weather was due to the emission of greenhouse gases.

When the ratio of carbon dioxide in the air doubles, the number of lightning bolts increase by 44 percent.

Authorities published many warnings about the weather. In Shanghai neon lights were ordered to be switched off, and in Beijing people were advised not to turn on computers or taps during the thunderstorms.

Last month, 141 people were killed by lightning in China, the highest monthly death toll since records began in 2000.