In the context of maritime and river ports, a "Signal 3"

 In the context of maritime and river ports, a "Signal 3" typically refers to a storm signal indicating that strong winds or rough weather conditions are expected, requiring vessels to take precautionary measures. However, this terminology can vary depending on the country's maritime warning systems.

In countries like the Philippines, for example, a Public Storm Warning Signal (PSWS) 3 means that winds of 121-170 km/h are expected within 18 hours. For maritime ports, this would mean that ships are advised to remain in port, and harbor operations are suspended due to hazardous conditions.

For river ports, the signal system might be different or more localized, depending on how the water body is affected by weather conditions like heavy rains, flooding, or strong currents.

If you're referring to a specific country or region's warning system, I can provide more precise information. Would you like more details on a particular system?