Rainstorm Warning System

The rainy season in Hong Kong is normally between April and September. Rain could be particularly heavy and persistent during May and June, causing severe traffic disruption and on occasions major floods and landslips resulting in casualties.

The rainstorm warning system is designed to alert the public about the occurrence of heavy rain which is likely to bring about major disruptions, and to ensure a state of readiness within the essential services to deal with emergencies. It is independent of other severe weather warnings such as tropical cyclone warning and landslip warning, which will be issued separately where necessary.

There are three levels of warning: AMBER, RED and BLACK.

The AMBER signal gives alert about potential heavy rain that may develop into RED or BLACK signal situations. There will be flooding in some low-lying and poorly drained areas. Key Government departments and major transport and utility operators are put on alert.

The RED and BLACK signals warn the public of heavy rain which is likely to bring about serious road flooding and traffic congestion. They will trigger response actions by Government departments and major transport and utility operators. The public will be given clear advice on the appropriate actions to take.

Once issued, the signals are broadcast over radio and television. For your own safety, listen to radio or television announcements for the latest information.

Please refer to the blog "Let's talk about rainstorm warning" (Part 1 and Part 2) regarding the purpose of and the factors being considered in establishing the rainstorm warning system, as well as some commonly asked questions.

GUIDE TO THE RAINSTORM SIGNALS

AMBER RAINSTORM SIGNAL

Heavy rain has fallen or is expected to fall generally over Hong Kong, exceeding 30 millimetres in an hour, and is likely to continue.

ACTION

Members of the public should take necessary precautions to reduce their exposure to risk posed by heavy rain, such as flooding. Going near easily flooded watercourses should also be avoided.
Parents, students, school authorities and school-bus drivers should listen to radio or television announcements on the weather, road and traffic conditions.
Candidates for public examinations should attend the examination as normal, but should listen to radio or watch television in case the weather deteriorates suddenly.
Farmers and fish pond owners, particularly those in low lying or flood frequented areas, should take the necessary precautions to minimise losses, which include checking and clearing the drainage system within and around the farm/fish ponds to ensure that all the drains are not blocked. Where possible, fish pond operators should reduce the water level of ponds which are likely to be flooded.

RED RAINSTORM SIGNAL

Heavy rain has fallen or is expected to fall generally over Hong Kong, exceeding 50 millimetres in an hour, and is likely to continue.

ACTION

Employees working outdoors in areas exposed to rain should suspend outdoor duties if weather conditions in those areas so warrant.
People who have to travel should carefully consider weather and road conditions.
If the RED signal is issued before working hours, employees should report for duty as usual, provided that transport services are available. Supervisors are encouraged to adopt a flexible attitude in case their staff have genuine difficulties in arriving at work on time.
If the RED signal is issued during office hours, employees working indoors should remain on duty as usual unless it is dangerous to do so. Employees in areas where transport services are about to be suspended can be exceptionally released at the discretion of the supervisor. In exercising their discretion, supervisors should take into account the weather and road conditions.

BLACK RAINSTORM SIGNAL

Very heavy rain has fallen or is expected to fall generally over Hong Kong, exceeding 70 millimetres in an hour, and is likely to continue.

ACTION

Stay indoors or take shelter in a safe place until the heavy rain has passed.
Employees working outdoors in exposed areas should stop work and take shelter.
People having no safe place to go may take temporary refuge in any of the special temporary shelters opened by the Home Affairs Department.
Employers are advised not to require their employees to go to work unless prior agreement on work arrangements during rainstorms has been made.
People who are already at work should stay where they are unless it is dangerous to do so.

SPECIAL ACTIONS TO BE TAKEN FOR RED/BLACK SIGNAL

Students who have not left for school should stay home. Those who have already arrived at school should remain in school until it is safe for them to return home.

If the RED/BLACK signal is issued when some students have set out for school -

If students learn the class suspension announcement on their way to school, they should decide whether to proceed to the school taking into consideration the rain, road, slope or traffic conditions.
School bus drivers should listen to radio broadcasts on the latest development of the rainstorm and ensure that students are taken to a safe place, usually the school they attend, unless road or traffic conditions ahead are unfavourable.
Schools should keep their premises open until the end of the normal school hours and implement contingency measures including arranging staff to look after those students who have arrived at school.

Candidates for public examinations should listen to radio or watch television for an announcement to be made by the Hong Kong Examinations and Assessment Authority.

Drivers should beware that there are likely to be serious road flooding and traffic congestion.

People should avoid going near easily flooded watercourses or passing through flooded areas. People whose home may be seriously flooded should consider evacuating their home until the rain has eased and flood water subsided.

Code of Practice in Times of Adverse Weather and “Extreme Conditions” (Labour Department)
What do rainstorm warning signals mean to you? (Education Bureau)
Tropical Cyclones and Heavy Persistent Rain Arrangements for Kindergartens and Day Schools (Education Bureau)
Tropical Cyclones and Heavy Persistent Rain Arrangements for Evening Schools (Education Bureau)

NOTES ON ISSUANCE OF THE WARNING SIGNALS

The rainfall criteria for the issuance of rainstorm warning signals are for guidance only. When prolonged rain occurs, the signals may be issued even if these rainfall criteria are not reached for individual hours.
The Observatory will make an effort to issue the AMBER signal a couple of hours ahead of anticipated heavy rain. However, this lead time may be considerably shorter in case the heavy rain develops rapidly. Not all AMBER signals will be followed by RED.
The Observatory will endeavour to issue the RED and BLACK signals before the specified rainfall levels are reached. However, local severe rainstorms are extremely difficult to forecast. The lead time will generally be very short. There will even be situations in which a RED signal is issued without a preceding AMBER. Similarly, a BLACK may be issued without a preceding RED.