What is a Rainfall Warning? Types of Rainfall Alert You Must Know

Nowadays, rain is more dangerous than it used to be. Climate change increases rainfall intensity, while environmental damage causes rainwater to flow freely into floods. Thus, government officials must broadcast a rainfall alert before rain falls. What is a rainfall warning?

During the rainy season, countries that are prone to rainstorms or heavy rain will actively issue rain warning alerts. These alerts let citizens know the severity of the coming rainfall. Therefore, they can prepare for the hydrologic disaster.

What is a Rainfall Warning?

Each country in the world has a weather alert system. This system is typically under the responsibility of the meteorological agency. However, in some countries, the disaster risk reduction (DRR) agency also operates the weather alert center.

Those agencies will issue a rain alert when heavy rain is imminent. What is a rainfall warning? A rainfall alert is a warning issued by the meteorological agency or DRR agency to authorities, local governments, and communities when there is a great risk of heavy rain.

Prolonged torrential rain can trigger other hazards, such as flash floods and landslides. Moreover, prolonged rainfall can damage infrastructure and buildings, make communities vulnerable to specific diseases, and disrupt transportation.

Consequently, issuing a rain alert several hours or a few days before the heavy rain occurs is crucial. This alert allows authorities to plan for preparation, response, and recovery action in advance. Moreover, the alert helps citizens prepare for the disaster by staying safe, cleaning drainage, and avoiding travel.

Types of Rainfall Alerts 

Rainfall alerts come in several levels. They indicate different levels of rainfall. Moreover, the rain warning levels have different color codes. Below are color-coded rainfall warnings and their meanings.

Blue Alert

Some weather alert systems have blue rainfall alerts. One of the government agencies that use this color code is IKCEST-DRR in China. When this authority issues the warning, it means rainfall will attain 50 mm in 12 hours or has already attained 50 mm and may proceed.

Government officials and communities in the affected areas must respond to the blue alert accordingly. The response guidelines for this warning are as follows.

• Check the drainage system and prepare the drainage.

• Drivers must stay safe by paying attention to traffic obstruction and road waterlogging.

• Schools must take action to ensure the safety of students.

• Government agencies must make some preparations to reduce the disaster risk. 

  Yellow/Amber Alert

In many countries, the yellow or amber rainfall alert sits at the lowest level.  What is a yellow rain warning? Below are the meanings of this alert in different countries.

• In the US, this alert means that the possibility of a hydrologic disaster increases significantly. However, the timing and location of this hazard are not yet known. When NWS issues this alert, people must plan measures to face the event.

• In Hong Kong, the amber alert indicates that heavy rain will reach over 30 mm in an hour or has already fallen and tend to continue. After the Hong Kong Observatory disseminates this alert, people must take measures to minimize exposure to heavy rain and flooding.

• In China, a yellow rainstorm warning indicates that rainfall is expected to reach 50 mm within six hours or has already attained that severity and may continue.

• In the Philippines, this alert means heavy rain with an intensity between 7.5 mm and 15 mm is expected to occur within an hour and will last for two hours onward.

  Orange Alert

Orange rain alerts are used in several countries, including the US, the Philippines, and China. What does this rain warning indicate?

• In the US, the orange rain warning means a hydrologic hazard is imminent. This hazard may cause significant inconvenience. Moreover, it may damage buildings and threaten life if people in the affected areas do not take precautions to face this disaster.

• In the Philippines, this rain alert indicates intense rainfall between 15 mm and 30 mm is expected to fall within an hour and will continue for two hours.

• In China, the orange rain alert means rainfall will attain 50 mm in three hours. People in the affected areas must stay indoors or delay their outdoor activities after receiving this alert.

Red Alert

The red rainstorm alert is common in many weather warning systems. The red rainfall warning means torrential rain will occur. The rainfall is expected to attain 30 mm to 100 mm within one to three hours. This hydrologic hazard poses a great threat to property and people.

Black Alert

Some countries use black to signify the highest level of rainstorm severity. This alert indicates very heavy rainfall exceeding 70 mm will occur within an hour and may continue.

After receiving this alert, people in the affected areas must stay safe by staying indoors and delaying travel. Moreover, those whose houses are in flood-prone areas must seek shelter in the temporary shelter provided by the local government.

What is a rainfall warning? It is an alert to warn people about the severity of the incoming rain. Authorities typically disseminate this alert via various channels, including wireless broadcast. However, governments will need cell broadcast technology to wirelessly disseminate the warning. To get this technology, please visit smsbroadcaster.com.