Climate of Learmonth

The North West Cape region has a dry climate with hot summers and mild winters. The average annual rainfall at Exmouth is 267 mm on an average of 26 days. Most rain occurs from May to July. There is considerable variation in the climate both within the region and from year to year.

The two main broadscale influences are the band of high pressure known as the sub-tropical ridge well to the south and a trough of low pressure that typically extends over the inland Pilbara in the warmer months. These combine to produce a general south or southeasterly wind regime for much of the year. Actual winds may vary considerably mainly due to the influence of afternoon sea breezes in the warmer months. These sea breezes are generally south to southwesterly on the western side of the peninsula and typically either southwesterly or northeasterly on the Exmouth Gulf side.

January is the hottest month. Learmonth has an average January maximum temperature of 38.0°C although further north on the peninsular temperatures are moderated by winds passing over the ocean. It is not uncommon for maxima to exceed 40°C for several consecutive days when winds blow from the inland Pilbara during summer. The highest temperature recorded at Learmonth is 47.7°C on 10 February 1977.

By contrast winters are mild with July average maximum and minimum temperatures being 24.0°C and 11.3°C respectively. Overnight temperatures rarely fall below 5.0°C. The lowest temperature recorded at Learmonth is 3.8°C on 19 July 1986.

Much of the annual rainfall occurs either during January to March and is associated with thunderstorms and tropical lows, or from May to July when tropical cloud bands originating to the northwest often bring heavy rains. May is the wettest month with a median value of 35.7 mm on four days. The highest daily rainfall recorded at Learmonth Airport is 226.6 mm on 26 January 1971 and the highest annual rainfall is 614.7 mm in 1961. Exmouth received a record daily rainfall of 304.6 mm on 4 June 2002. In the surrounding area, the highest daily fall occurred on 30 March 1964 when 417.8 mm fell at Yardie Creek during tropical cyclone Kate. The highest annual total is 832.2 mm at Vlamingh Head in 1923 when heavy rains fell in January, March and April.

A tropical cyclone causing strong winds, high seas and heavy rain affects the North West Cape area about once every two years on average. Cyclones can be experienced during the months from December to April but are most common in February and March (75 % of occurrences). The semi-enclosed waters of Exmouth Gulf have the potential to cause large and damaging storm surges, particularly at the southern end of the gulf. During the cyclone on 2 February 1945 a barge was left stranded on the RAAF airstrip following a storm surge. Winds reported to have reached 190 km/h during this cyclone caused widespread damage throughout the area with virtually every structure at the air base and at Exmouth Gulf station affected. Most cyclones approach the area from the north or northeast. The highest wind gust recorded at Learmonth Airport is 267 km/h on 22 March 1999 during severe tropical cyclone Vance. This is also the highest wind gust measured on the Australian mainland.

The relative humidity varies from about 43-68% at 9 am and from about 25-40% at 3 pm, the lower values occurring in the second half of the year. Evaporation is high and varies from 3.9 mm per day in June to 12.5 in December.