Read the passage carefully and choose the correct answer.

 Traffic jams in Vietnam only frequently take place in Hanoi capital and Ho Chi Minh City. Vietnamese people seem be accustomed to traffic congestion, even miss it whenever they go to other places.

There is no fixed rules for the time the traffic jams to happen but it is worst during the rush hour when everyone is in a hurry to get to work or come back home. Apart from peak hours, the time between 9 am to 10 am and between 3 pm to 4 pm also witnesses long lines of vehicles, mainly motorbikes, struggling to get out of narrow streets. Whenever it rains, the traffic jam gets more terrible with the joining hand of flooding. Taxis are extremely hard to catch or wave during the downpour. However, it only takes about 30 minutes on average for a stand still and 2 hours to get through the worst, not really bad compared to that of other countries.

What happens with the traffic congestion when it rains?