Turbulence

Intensity	Aircraft Reaction	Symbol
Light	Loose objects in aircraft remain at rest.
Moderate	Unsecured objects are dislodged. Occupants feel definite strains against seat belts and shoulder straps.
Severe	Occupants thrown violently against seat belts. Momentary loss of aircraft control. Unsecured objects tossed about.
Extreme	Aircraft is tossed violently about, impossible to control. May cause structural damage.

Icing

Intensity	Aircraft Reaction	Symbol
Trace	Ice becomes perceptible. Rate of accumulation slightly greater than sublimation. Deicing/anti-icing equipment is not used unless encountered for an extended period of time (over 1 hour).
Light	The rate of accumulation may create a problem if flight is prolonged in this environment (over 1 hour). Occasional use of deicing/anti-icing equipment removes or prevents accumulation. It does not present a problem if this equipment is used.
Moderate	The rate of accumulation is such that even short encounters become potentially hazardous, and use of deicing/anti-icing equipment or diversion is necessary.
Severe	The rate of accumulation is such that deicing/anti-icing equipment fails to reduce or control the hazard. Immediate diversion is necessary.