Common climate and weather terms Climate and weather terms Above Average In climatology, this refers to the top third of data recorded in the standard 30 year normal period. For example, if above average rainfall is recorded, this indicates that the rainfall lies in the highest third of rainfall recorded in the standard 30 year normal period, i.e it was much wetter than normal. Anomaly Departure from normal, difference from the average. Anticyclone An area of high pressure around which the winds circulate anti -- clockwise in the Southern Hemisphere. Also called a 'high'. Autumn The season March, April, May in the Southern Hemisphere. This season is characterised by decreasing temperatures in most areas of New Zealand. Barometric Pressure The pressure exerted by the atmosphere at a given point. It can be thought of as the weight of air in the column above you. Its is normally measured in inches of mercury, millibars, or hectopascals. It is measured with a barometer. Below Average In climatology, this refers to the bottom third of data recorded in the standard 30 year normal period. For example, if below average rainfall is recorded, this indicates that the rainfall lies in the lowest third of rainfall recorded in the standard 30 year normal period, i.e. it was much drier than normal. Climate The historical record and description of average weather in a region or place. Statistics are normally derived from several decades' worth of data. The word is derived from the Greek word klima, meaning