Climate of Meekatharra

Meekatharra has a dry climate with hot summers and mild winters. The annual average rainfall is 237 mm on an average 46 days and while the average rainfall is fairly well distributed throughout the year, there is considerable annual variation.

The climate of the region is strongly influenced by a band of high pressure known as the sub-tropical ridge, and in the warmer months by a trough of low pressure that extends southwards from the heat low in the tropics. For most of the year the ridge is located to the south, and east to southeast winds prevail. Occasionally during the cooler months the ridge moves far enough to the north to allow cold fronts to pass over the area. While most fronts bring little rain to Meekatharra they are sometimes linked to tropical cloud bands which deliver the most reliable rains from May to July.

By contrast winters are mild with the July average maximum and minimum temperatures being 18.8C and 7.4C respectively. Overnight temperatures fall below 5C about once a week in a typical winter. Such temperatures occur on clear nights following a day of cool southerly winds.

June is the wettest month with an average rainfall of 33.2 mm on six days. The other wet months are January to March when thunderstorms can often produce heavy localised falls in short periods. Although rare, tropical lows or weakening tropical cyclones that usually originate off the Pilbara coast can bring widespread rain to the region. The highest daily rainfall occurred on 13 June 1989 when 114.4 mm was recorded from a 'northwest' cloud band. The highest annual total is 515.6 mm in 1915 and resulted from thunderstorms in January and February.

It is not uncommon for very little rain to occur for months particularly during spring. One of the driest periods occurred from March 1935 to December 1936 when just 127 mm fell.

January is the hottest month. The average temperature is 38.1C, but temperatures above 41C typically occur once a week when hot, dry, northeast to northwesterly winds arrive. High temperatures are usually followed by a cool change from the south and occasionally a thunderstorm.

With only an average of 46 wet days each year the air is generally dry, particularly in summer when afternoon relative humidity typically drops below 20%. Even during the cooler months the average 9 am relative humidity is only about 60%. Half of the annual evaporation of 3576 mm occurs from November to February. The average daily evaporation rate in January is 16.5 mm per day while on a hot blustery day it can be well over 20 mm. During winter the average daily evaporation decreases to 3.7 mm.