Ships and aircraft are always keeping watch on the weather as it creates special problems for them. At sea, waves and swell produced by storms are the major hazards. A storm can transform the sea's surface into an unpredictable force - waves of up to 18 m (60 ft) are fairly common. The largest documented wave measured 34 m (112 ft) in height.

In the air, the main dangers are hailstones and strong upcurrents and downdraughts produced by storms. Hailstones more than 1 cm in diameter can damage an aircraft. Pilots are trained to avoid the dangers of hail by flying around rather than beneath storm clouds. Sudden changes in wind velocity are one of the most dangerous hazards facing aircraft that are coming in to land. A thunderstorm can produce unexpected vertical downbursts of 90 km or more. Flying through a downburst may cause the aircraft to crash.

Thick fog which can conceal coastlines and runways is another common hazard. Lighthouses built on the coast or on offshore rocks use both light and sound to warn ships of fog. The sound of a lighthouse foghorn can be heard for about 30 km (20 miles) over water. Some airports have fog dispersal systems which use hot air to evaporate the fog on the main runway for clear take-offs and landings.