What Does HZ Mean in a METAR?
HZ means haze. It stands for HaZe.
HZ in a real report
HZ
That reads as haze.
What it changes for you
Haze is the restriction that does not behave like the others. It is dry particles, so it does not thicken as the air cools and it does not burn off with the sun.
The practical consequence is slant visibility. Reported visibility is measured horizontally near the ground. Looking down through a haze layer on approach can be much worse than the number suggests, which is the classic trap on a hot afternoon with good reported visibility and a low sun.
Telling it apart in the report
Check the temperature and dew point spread. Mist needs a small spread; haze does
not care. A report showing 4 miles in HZ with a 15 degree spread is not going
to become fog, and a report showing 4 miles in BR with a 1 degree spread very
well might.
Related codes
Decode a report containing this code
Paste a METAR, TAF, PIREP or SIGMET into the WxDecoder decoder. Every group comes back in plain English. The raw code sits beside it, so you can check the decode rather than trust it.
Frequently asked questions
What is the difference between HZ and BR in a METAR?
Haze is dry particles such as dust and pollution. Mist is water droplets. Haze does not respond to a small temperature change, and mist does, which is why haze can sit at the same visibility all day while mist thickens toward evening.
Does haze count as instrument conditions?
It can. Haze is reported when visibility is restricted, and the flight category is worked out from the reported visibility regardless of what is causing it. Three miles in haze is the same category as three miles in mist.