September 2014 Review - Sydney

It was a rather cool September for Sydney in 2014 - or at least it was until the final three days of the month. The month had been on track to record the lowest average maximum for a September since 1997, but late warm temperatures, especially on the final two days, pushed the average to similar levels seen since 2000. Both the average minimum and maximum were comfortably above the long term average. Rainfall, on the other hand, was below average.

The graph below shows that the averages for September 2014 weren't too far off figures seen in recent years.

September averages at Sydney Airport for the period 2009-2014 plus the long term average

Cold weather seen in August continued into the first week of September. The first seven days of the month at Sydney Airport had an average maximum of only 17.7C. This was almost 3C lower than the 20.4C measurement from the same period in 2010, the next lowest since 2009. In contrast, last year saw an average of 25.8C during the same period.

The average maximum after September 27 sat at 20.4C, but the final three days increased the average to 21.5C. Based on that, it's not a surprise that September 2014's highest temperature at the Airport came on the very last day of the month. The 34.2C recording was the equal sixth highest September temperature since records began in 1939. The all time record is 35.6C from 2000. The 29th saw the 12th highest on record with 33.5C. This was the first instance on record for two consecutive September days above 32C.

The highest minimum came on September 25. The 15.9C recording was in the middle of respective figures since 2009.

The lowest temperature of the month was shared by the 2nd and 20th. It dipped to 8.7C on both days. This was the equal second highest such figure since 2009. The lowest maximum was seen on the 3rd. It reached only 15.1C then. As mentioned in a previous post, the period across September 3, 4 and 5 was the first instance of three consecutive September days below 15C since 1995.

Daily minimums and maximums against rainfall at Sydney Airport for September 2014

With a long term average of 60.2mm, September is historically the driest month of the year at the Airport. The start of September this year showed signs that the average might be surpassed, but despite recording 14 days of rain during the month, the monthly total of 41.6mm was only about two-thirds the long term average. Since 1996, only one September has recorded more than 100mm; 2006 saw 144.2mm.

The longest rain day streak was eight, with those days tallying 30.0mm. That was from the very start of the month. It was also part of the remarkable run from mid-July that included only one dry day across a 24 day period. September 6 and 7 both saw 9.2mm, the highest daily total for the month. Only one other day saw more than 5mm of rain; September 10 with 5.6mm. The longest streak of dry weather was the four day period from the 17th to the 20th.

Once again the average for the highest daily gusts was down on last year's figures. An average of 48.2km/h was the figure for 2014, compared to 50.1km/h last year. The strongest gust of the month came on the 3rd, a 83km/h south-southwesterly. There were four days with a maximum gust above 60km/h, compared to seven in September last year. The 14th and 19th shared the weakest maximum gust figure of the month at 31km/h.