Tuesday, 1 March 2011 - Seasonal Climate Summary for New South Wales - Product code IDCKGC15R0

NSW in summer 2010-11: Wettest summer in 29 years

• 5th wettest summer on record for NSW.
• 3rd wettest summer on record in the Murray-Darling Basin.
• Well above average night time temperatures, 14th warmest minimums on record.

Extremes Maps Records Summaries Important notes the top

Rainfall

NSW recorded 272.2mm of rainfall during summer, well above the historical average of 170.4mm and the 5th wettest summer on record for NSW, the wettest since 1983. Rainfall was above average throughout the season, with particularly wet conditions in western regions during January and February as conditions in the north and east began to dry. In addition, the Murray-Darling Basin recorded 270.6mm during summer, its third wettest summer on record following the very wet periods in 1973/4 (286.8mm) and 1975/6 (336.1mm). The high rainfall followed record-breaking falls during spring, a consequence of the strong La Niña event that developed in the Pacific Ocean over 2010.

Several very significant rainfall events during summer brought major flooding to NSW, with 84 Natural Disaster Declarations during the season. The first major event occurred during the first weeks of December, as heavy rains caused flooding across southern and western NSW. Widespread evacuations occurred with over a hundred flood rescues and major infrastructure damage in key rural centres including Orange, Dubbo, Wagga Wagga and Tamworth. Reports suggested this was the most severe flooding in 50 years in some regions.

The second major flood event occurred over the last week of December and early January, as heavy rain on the north coast of NSW and southern Queensland caused significant flooding in northern parts of the state. Hundreds of people were evacuated and thousands isolated during the first weeks of January, with further flooding in western regions throughout January and February as floodwaters progressed southward through the Darling river system.

The third major event occurred between the 12th and 14th of January, as a trough system over central NSW directed very heavy rainfall into the west of the state, with many areas experiencing record-breaking totals and some riverine flooding, although flooding was most severe in Victoria. Finally, a similar trough system between the 2nd and 6th of February brought further rain to western and southern parts of NSW, resulting in further riverine flooding along the Murray.

Some sites had their highest total summer rainfall on record. Some sites had their lowest total summer rainfall on record.

See a map of rainfall deciles.

Temperature

The average temperature in NSW was 24.5 °C during summer, slightly above the historical average of 24.2 °C. Temperatures were warmest in January, which was the 11th warmest on record for mean temperatures, with close to average temperatures in February but very much below average temperatures in December, the 10th coolest on record. The average temperatures were a result of generally below average maximum temperatures across almost all of the state but warmer than average nights, particularly in the east.

Maximum temperatures averaged 29.9 °C during summer, 0.3 °C below the historical average of 31.2 °C, with the majority of the state experiencing temperatures 1 to 2 °C below average. This was a result of the significant rainfall during the season, particularly in western regions, with very cold conditions in December but warmer temperatures in January and February. Warmer conditions were experienced in coastal regions associated with warm sea surface temperatures, particularly in the metropolitan and hunter regions. Daily temperatures varied significantly during the season, with some very warm conditions experienced on the 26th and 27th of January and in eastern regions between January 31 and February 6, but very cold conditions between the 19th and 21st of December and record-breaking cold at Broken Hill as a cool change entered the state on February 6.

Night time temperatures were warmer during summer with a statewide average of 18.0 °C, 0.9 °C above the historical average of 17.1 °C and the 14th warmest on record. Unlike maximum temperatures, minimums were only slightly below average in December, with well above average temperatures in January and February, with almost all of the state recording above average minimums. Minimums were particularly warm in eastern parts of the state, with most of the coastal region experiencing temperatures more than 1 °C above average and several stations experiencing their warmest average summer minimums on record during a heatwave in early February. However, very cool conditions between the 20th and 21st of December also broke several summer records for coolest minimums.

Some sites had their highest summer temperature on record. Some sites had their coldest summer day (lowest maximum temperature) on record. See a map of maximum temperature anomalies.

Some sites had their lowest summer temperature on record. Some sites had their warmest summer night (highest daily minimum temperature) on record. Some sites had their highest summer mean daily minimum temperature on record. See a map of minimum temperature anomalies.

Other phenomena

Conditions were windiest during December and February, with gusts above 100km/hr recorded on December 15, 19, 20, and 27 and on February 1, 4, 5 and 19, but a maximum gust of just 85km/hr on the mainland in January. The strongest wind gust recorded during the season was 130km/hr at Thredbo on January 19.

Extremes Maps Records Summaries Important notes the top

Extremes Maps Records Summaries Important notes the top

Extremes Maps Records Summaries Important notes the top