Definition
An obscuration to visibility caused by very fine, dry particles suspended in the atmosphere — typically dust, smoke, or pollutants — that scatter light and reduce horizontal visibility, even when relative humidity is low. Reported as HZ in METARs and TAFs when these particles, individually invisible to the eye, collectively give the air a milky or opalescent appearance.
Plain English
A thin, dry haze in the air made of tiny particles like dust or smoke. You can't see the particles themselves, but together they make the air look slightly milky and cut down how far you can see.
Context Anchor
Seen in coded airport weather reports and forecasts, usually near the reported visibility.
Derivation
HZ is a shortened aviation weather code for haze. Weather reports use compact codes so pilots can read conditions quickly.
Why Pilots Care
Haze can bring visibility below VFR minimums and force pilots to adjust routing or delay departure.
Grounding Statement
In haze, the air can look slightly milky or faded even when there is no cloud directly in front of you.
Intuition Check
HZ does not mean fog or cloud. It means dry particles in the air are reducing how clearly you can see.
Example Sentence 1
The METAR reported 5SM HZ, so the pilot expected reduced visibility on the descent into the valley.
Example Sentence 2
Wildfire smoke created widespread HZ that reduced visibility along the entire route.