Beijing ran for cover as the city witnessed its heaviest rainfall this year yesterday, with a precipitation of 19 mm.

Rain lashed the capital at 5 am, just minutes after the Beijing meteorological bureau signaled a yellow warning of thunder and lightning at 4:35 am. It continued throughout the day, throwing daily life into disarray, with several streets clogged with water.

The urban area of Beijing stayed especially wet, with an average precipitation of 26 mm, the bureau said.

According to the bureau, the downpour was the result of an "intense collision of cold and warm air, which was the strongest this summer".

It has been rare for heavy rain to continue through the day, the bureau said, adding it was the "heaviest downpour since October".

The weather today, however, is expected to be sunny, with the temperature rising to 30 C from 22 C yesterday, the weather department said.

On Friday, the bureau had warned students sitting for the college entrance exam, which concluded yesterday, to prepare for a storm.

Though the morning rush hour went by without many hiccups on the city's subway system, the public transportation company added 200 backup buses to its fleet. About 5,000 volunteers stationed at various stops helped maintain order.

Most of the extra buses and volunteers were sent for routes leading to the exam centers.

Many students still reported late for the examination, which kicked off at 9 am, claiming to be stuck in severe traffic.

From 8:30 am to 9 am, 143 phone calls were made to 122, a transportation hotline for help, asking for alternate routes to get to examination centers.

Questions:

1. What warning did the Beijing meteorological bureau issue?

2. According to the bureau, what caused the heavy downpour?

3. What is the transportation hotline number?

Answers:

1. A yellow signal.

2. An intense collision of cold and warm air.

3. 122.