Final answer:
The most dangerous icing condition outside of thunderstorms is clear ice, which poses a significant threat to aircraft due to its heavy accumulation and impact on aircraft performance. This severe weather hazard is exacerbated by storm conditions with unpredictable localized electric fields.
Step-by-step explanation:
Outside of icing that can form in thunderstorms, the icing condition that is considered the most dangerous is clear ice. This type of icing forms when supercooled water droplets in the atmosphere come into contact with the surface of an aircraft. The situation presents a potential for extreme physical danger due to the heavy accumulation of clear, hard ice, which can drastically affect the performance and control of the aircraft.
In storm conditions, clouds form and localized electric fields can be larger and reversed in direction, leading to unpredictable weather patterns and increased risk hazard from icing. These conditions are influenced by the regional environment, and variations are possible, demonstrating the uncertainty over whether a serious fire or hazard awaits after an alarm signal. Pilots must be vigilant in these situations to maintain safety.