Most areas of the Sydney Basin received less than half of their average September rainfall, which contributed to cools night but warm days. Eastern Australia was dominated by high pressure systems during the past month, which maintained clear skies with little rainfall. East of the Great Dividing Range, most areas of New South Wales gained less than half of their average September rainfall. Central and northwest parts of the state were closer to average in terms of rainfall, mainly a result of thunderstorms. Sydney Observatory Hill recorded just 23.8mm of rain during September, which is 45mm below the historical average but was not as dry as 2009 when only 16mm fell during the month. The city recorded an average minimum temperature of 12 degrees during September, which was one above the long-term average but still the coldest in eight years. The cool overnight temperatures were more noticeable in western Sydney, where the ocean temperatures have less of an impact. Bankstown recorded an average minimum of 7.9 degrees during September, its coldest in 23 years. There was plenty of sunshine through the month with the city recording an average of 9.2 hours of sunshine during September, which was well above the long-term norm of 7.2 hours. The above average amount of sunshine contributed to warmer days. Sydney Observatory Hill averaged daytime temperatures of 22.4 degrees during September, which was more than two degrees above the long-term average. For the month to come, the drier and warmer than normal conditions are expected to continue. A developing El Nino pattern adds weight to the drier conditions and there has been a significant build-up of heat over the nation's interior, which brings increased potential for hot days. Sydney has already experienced the impacts of the heat build-up within the past week, when northwesterly winds dragged the warm interior airmass into the east on Friday. The city hit 33 degrees on Friday, which was the warmest September day in six years and we can expected more of this in the months to come.