What is a hazard associated with thunderstorms that can affect aircraft?

Wind shear is a significant hazard associated with thunderstorms that can adversely affect aircraft. It refers to a sudden change in wind speed or direction over a short distance. In the context of thunderstorms, these changes can be abrupt, often occurring as strong downdrafts or updrafts within and around the storm. When an aircraft flies through regions of wind shear, it may experience rapid changes in lift and drag, leading to potential loss of control and difficulties in maintaining a stable flight path.

This hazard is particularly dangerous during takeoff and landing phases when aircraft are at lower altitudes and more susceptible to such dramatic wind changes. Pilots must be aware of wind shear alerts and monitor weather reports to prepare for and mitigate its impacts during flight operations.

In contrast, the other options do not pose similar hazards; calm winds are generally favorable for flying, high altitudes may not be directly related to thunderstorms, and clear skies suggest stable weather conditions, which are typically not associated with thunderstorm activity.