A gale is a very strong wind. The Beaufort scale is a way to measure weather conditions. It is based on observations. The first level of the scale that uses the word gale is 7 beaufort (of a total of 13 steps). There are other definitions as well. The U.S. Government's National Weather Service defines a gale as 34 to 47 knots (63 km/h to 87 km/h or 39 miles per hour to 54 miles per hour) of sustained surface winds. Forecasters usually issue gale warnings when they think there will be winds of this strength.