Which weather phenomenon poses the greatest risk of causing a loss of control for a small UAS?
ALight drizzle and mist reducing visibility to 4 miles
BThunderstorms with associated turbulence, lightning, and wind shear✓
CHigh humidity reducing air density by 3%
Why →Thunderstorms combine multiple hazards: severe turbulence and wind shear capable of overwhelming flight controller corrections, lightning that can directly strike or induce currents in the aircraft, hail, and rapid visibility changes. A microburst from a nearby thunderstorm can produce downdrafts exceeding 6,000 fpm, far beyond any sUAS's ability to compensate.
The trap →Light drizzle at 4 miles visibility is marginal but legal and manageable. A 3% density reduction is measurable but minor. Neither comes close.
Field note →The rule is simple: if you can see, hear, or detect a thunderstorm within 20 miles on radar, do not fly. The associated wind shear field extends far beyond the visible storm cell.
SOURCE → PHAK Chapter 12, Weather Theory / FAA Remote Pilot Study GuideCHECKED JUL 16ACS III.A.K1MED