AIM ¶ 7-1-16 — Rain and Ice Pellet Intensity
AIM 7-1-16 explains how to estimate light, moderate, and heavy rain and ice pellet intensity. Study guide for pilot written tests, oral exams, and checkrides.
In Plain English
AIM 7-1-16 gives pilots and observers a practical way to estimate precipitation intensity for rain and ice pellets without specialized equipment. Knowing how to describe what you're seeing matters for PIREPs, runway condition assessments, and decisions about takeoff, landing, and diversion.
Rain intensity:
- Light: Scattered drops that do not completely wet an exposed surface, regardless of duration; individual drops are easily seen.
- Moderate: Individual drops are not clearly identifiable; spray is observable just above pavements and hard surfaces.
- Heavy: Rain falls in sheets; drops are not identifiable; heavy spray rises several inches above hard surfaces.
Ice pellet intensity:
- Light: Scattered pellets that don't completely cover a surface; visibility is not affected.
- Moderate: Slow ground accumulation; visibility reduced to less than 7 SM.
- Heavy: Rapid ground accumulation; visibility reduced to less than 3 SM.
This guidance is informational, not regulatory — but it standardizes the language pilots use when reporting weather to ATC and Flight Service.
AIM Source Text
FAA AIM ¶ 7-1-167-1-16. 7-1-16. Estimating Intensity of Rain and Ice Pellets
Rain 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. Moderate. Individual drops are not clearly identifiable; spray is observable just above pavements and other hard surfaces. Heavy. Rain seemingly falls in sheets; individual drops are not identifiable; heavy spray to height of several inches is observed over hard surfaces. Ice Pellets Light. Scattered pellets that do not completely cover an exposed surface regardless of duration. Visibility is not affected. Moderate. Slow accumulation on ground. Visibility reduced by ice pellets to less than 7 statute miles. Heavy. Rapid accumulation on ground. Visibility reduced by ice pellets to less than 3 statute miles.
Oral Exam Questions a DPE Might Ask
Q1How would you describe heavy rain when filing a PIREP?
Per AIM 7-1-16, heavy rain is reported when rain seemingly falls in sheets, individual drops are not identifiable, and heavy spray is observed to a height of several inches over hard surfaces.
Q2What visibility criteria distinguish moderate from heavy ice pellets?
Per AIM 7-1-16, moderate ice pellets reduce visibility to less than 7 statute miles with slow ground accumulation, while heavy ice pellets reduce visibility to less than 3 statute miles with rapid accumulation.
Q3How is light rain distinguished from light ice pellets in terms of surface effect?
Per AIM 7-1-16, light rain consists of scattered drops that do not completely wet an exposed surface regardless of duration, while light ice pellets are scattered pellets that do not completely cover an exposed surface and do not affect visibility.
Related Paragraphs in AIM Chapter 7