Why is a "weather brief" important before a flight?

A weather brief is essential before a flight because it provides the current weather conditions and forecasts, which are crucial for ensuring safety and making informed decisions during the flight. Pilots rely on accurate weather data to assess potential hazards such as thunderstorms, icing conditions, turbulence, and visibility issues that could impact the flight's route and safety. Understanding both the current weather and expected changes enables pilots to plan accordingly, choose appropriate altitudes, and anticipate any need for alternate routes or airports in response to changing conditions.

The other options, while valuable in different contexts, do not directly relate to the immediate operational safety and decision-making aspects that a weather brief provides. Flight regulations, emergency contact information, and aircraft performance metrics are important, but they do not equip pilots with the situational awareness necessary for addressing weather-related challenges that may arise during a flight.