The strong operation of the cold air will trigger rain, hail and lightning.
The weather agency also issued weather warnings of the whole country from October 5- 10.
During this week, both the Northern and Central regions are forecast to suffer days of medium- heavy rains, thunderstorm and maximum temperature between 27 degrees Celsius and 32 degrees Celsius.
The same weather condition is also warned for the Southern and Central Highlands provinces and cities from October 5-11, with the highest temperature of 29-33 degrees Celsius.
Water level on the upstream Mekong River would tend to reducing gradually in the first days of this week, after that it is predicted to rise following high tides.
From October 10-11, the highest water levels on the downstream Mekong and Saigon Rivers are able to reach alert level 1-2, even exceeding alarm level 2 in some places.
