AIM 7-1-16 Estimating Intensity of Rain and Ice Pellets
Chapter 7. Safety of Flight · Section 1. Meteorology
A reference copy of the official AIM text for study. It is not legal advice or an FAA interpretation; always confirm against the current official source.
a. Rain
1. Light. From scattered drops that, regardless of duration, do not completely wet an exposed surface up to a condition where individual drops are easily seen.
2. Moderate. Individual drops are not clearly identifiable; spray is observable just above pavements and other hard surfaces.
3. Heavy. Rain seemingly falls in sheets; individual drops are not identifiable; heavy spray to height of several inches is observed over hard surfaces.
b. Ice Pellets
1. Light. Scattered pellets that do not completely cover an exposed surface regardless of duration. Visibility is not affected.
2. Moderate. Slow accumulation on ground. Visibility reduced by ice pellets to less than 7 statute miles.
3. Heavy. Rapid accumulation on ground. Visibility reduced by ice pellets to less than 3 statute miles.