Košava ([kɔ̌ʃaʋa]) is a cold, very squally southeastern wind found in Serbia and some nearby countries. It starts in the Carpathian Mountains and follows the Danube northwest through the Iron Gate region where it gains a jet effect, then continues to Belgrade. It can spread as far north as Hungary and as far south as Niš.
In the winter, it can cause temperatures to drop to around -30 °C. In the summer, it is cool and dusty. It varies diurnally, and is strongest between 5:00 and 10:00 in the morning. Košava is usually caused by a low pressure zone over the Adriatic Sea and a corresponding high pressure zone in southern Russia.
The name is also used traditionally in northwestern Bulgaria to mean a southeastern or eastern wind. There exists the saying: "When košava blows, the Nišava freezes".
Speed and occurrence of the Košava wind have declined in the period 1949-2010. The same study showed that Košava usually lasts for 2 or 3 days, 1-day events being very rare.
Koshava wind blows when there is a high air pressure (an anticyclone) over eastern Europe and/or west Asia and a low pressure (a cyclone) over the middle and/or western Mediterranean region. The strong anticyclone, however, is the main trigger for the Koshava wind. Koshava is also a gap flow windstorm. Koshava's occurrence can be successfully forecast using the across-mountain mean sea level pressure and potential temperature differences.