Definition
An ATC phrase used to describe radar returns that may be either weather (precipitation) or chaff (small reflective strips released by military aircraft), when the controller cannot positively distinguish between the two on the radar display.
Plain English
When a controller sees something on radar that could be rain or could be metallic strips dropped by military aircraft, and they can't tell which, they describe it to pilots as 'weather and chaff information' rather than guessing.
Context Anchor
A pilot may hear this from ATC when a controller sees weather or chaff on radar near the aircraft’s route.
Derivation
Chaff comes from the old English word for husks of grain — small, light bits that scatter easily. Military chaff works the same way: thin metallic strips released into the air to scatter and reflect radar energy, originally used to confuse enemy radar. The phrase pairs 'weather' with 'chaff' because both produce similar fuzzy returns on ATC radar.
Why Pilots Care
Allows pilots to avoid areas of hazardous weather and prevents mistaking chaff returns for actual precipitation or traffic.
Grounding Statement
If ATC sees a patch on radar that is not an aircraft but could matter to your flight, they may pass weather and chaff information to help you stay aware.
Intuition Check
Chaff does not mean grain waste here. In aviation, chaff means small radar-reflecting material in the air, usually released by military aircraft. Weather here does not mean a full forecast. It means weather that ATC is observing or reporting in relation to your flight path.
Example Sentence 1
Center advised, 'Cessna 23X, weather and chaff information twelve o'clock, two zero miles, moving east.'
Example Sentence 2
We requested weather and chaff information and learned of several chaff corridors active north of the airport due to military training.