Wind gusts
Wind gusts peak gusts
A gust is a brief increase in wind speed. This peak can be much stronger than the wind averaged over several minutes.
Why wind suddenly speeds up
Air does not move as a perfectly steady stream. Swirling eddies mix faster and slower air. Buildings, trees and hills create this turbulence. Showers and thunderstorms can also carry faster air from higher levels down to the ground.
How to read a gust forecast
Weather stations often record gusts as the highest three-second average within an observation period. Check the period in a forecast too: an hourly gust value describes the expected peak during that hour.
- Mean wind 20 km/h: the wind averaged over a longer period.
- Gusts 50 km/h: individual short peaks may be much stronger.
- Do not add the values: the gust in this example is 50 km/h, not 70 km/h.
Why gusts matter
A sudden crosswind can push a bicycle sideways or slam a door. Under otherwise similar conditions, wind force increases roughly with the square of speed: twice the speed produces about four times the force. Brief peaks therefore matter greatly for loose objects and branches.
Buildings can redirect and accelerate wind locally. An area forecast cannot predict every gust at a street corner. A low mean wind does not rule out strong thunderstorm gusts.