What factors can increase the effectiveness of deice fluid?

The effectiveness of deice fluid can be significantly influenced by a combination of environmental and operational factors. In this context, the option highlighting heavy precipitation and high winds stands out because these conditions directly affect the application and longevity of deice fluid on aircraft surfaces.

When heavy precipitation occurs, particularly in the form of rain or wet snow, deice fluid must work harder to prevent ice and snow accumulation. High winds can also aid in the evaporation of moisture, which can enhance the fluid's ability to adhere to surfaces and perform its function effectively. Therefore, the dynamic nature of these conditions can result in a more efficient application and maintenance of deice fluid, ensuring that the aircraft remains safe for operation in winter conditions.

Other options present conditions that may not promote the ideal performance of deice fluid. For example, high humidity and low temperatures can lead to the fluid freezing or becoming less effective. Similarly, calm winds and light precipitation might not create conditions severe enough that would necessitate strong effects from deice fluid, while low aircraft skin temperature and jet blast might contribute to inadequate coverage or ineffective application.