Föhn wind
A warm, dry, often gusty downslope wind on the lee side of a mountain range — Föhn in the Alps, Chinook in the Rockies, Halny in the Tatras.
Also known as: foehn, chinook, zonda, halny, downslope wind
A Föhn (or Chinook, or Zonda, or Halny — same physics, different mountain) forms when air is forced over a ridge, loses moisture as rain or snow on the windward side, and warms by compression on the way down. By the time it reaches the lee-side valley it’s dry, warm, and accelerated.
Trademark behaviours:
- Sudden warming of 10–20 °C in a few hours
- Gust factors of 1.4–1.7 — handful for kites and wings
- Famous for melting snow in winter and ramping fire risk in dry seasons
- Often turbo-charges sessions in valleys oriented along the flow (Lake Garda’s Föhn days, Tatra foothill spots on Halny)
Regional names you’ll meet on forecasts: Föhn (Alps), Chinook (Rockies), Zonda (Argentine Andes), Halny (Tatras), Bergwind (South Africa), Santa Ana (California, dry variant). The wider family of mountain-shaped winds is covered in Types of Wind.
Related terms
- Katabatic wind A gravity-driven wind formed when cold, dense air drains downhill off a high plateau or glacier — often offshore, often ferocious.
- Gradient wind The large-scale wind driven by pressure differences between weather systems — the synoptic background flow that everything else rides on top of.
- Gust factor The ratio of peak gust to average wind — the single most useful number for telling smooth wind from a fight.