Monday, 14 October 2013 - Monthly Climate Summary for Sydney - Product code IDCKGC15L0

Sydney in September 2013: Warmest September on record

• Maximum temperatures break previous September record by 1 °C
• Records broken for warm days, cool nights, warm spells
• Below average rainfall; wettest day since June.
• Early start to bushfire season

Extremes Records Summaries Important notes the top

Rainfall - Below average rainfall, one rain event

Sydney Observatory Hill recorded 35.8 mm of rain during September, half the historical average of 68.6 mm. The rain fell over only four rain days (average 11 days), the fewest since 2009, all of which fell during the middle of the month.

The only day with more than 5 mm of rain was on the 17th, when a complex low pressure trough with embedded lows produced heavy rain across the coast. Daily totals reached 32.2 mm at Observatory Hill, the heaviest rain day since June. Falls were locally heavier in the eastern suburbs, some of which consequently recorded above average rainfall for the month. The heaviest total was 88.2 mm at Randwick Bowling Club, its wettest September day on record.

Temperature - Warmest September on record

September was the warmest on record for Sydney, with a substantial number of records broken at Observatory Hill. Mean temperatures broke records at all six major temperature stations in the city, a consequence of widespread maximum temperatures more than 3 °C above normal and minimum temperatures more than 1 °C above normal, and persistent warm weather during the month.

The average maximum temperature at Observatory Hill was 24.4 °C, 4.4 °C above the historical average for September and 1.1 °C above the previous September record (23.3 °C in 1980), with temperatures more typical of November weather (average 23.6 °C).

Daytime temperatures were persistently warm during the month, with only three days dropping below 20 °C associated with a mid-month rain event, an equal record with September 2012 (average 17 cool days). This included 20 consecutive days above 20 °C between August 24 and September 12, the longest such spell on record for September and two weeks earlier than the previous record (19 days 7-25 September 2001).

There were also several very warm days during the month. Seven days reached at least 28 °C during the month, well above the historical average of 1 warm day and the most on record (previous record 6 days in 1928). Three of these days reached 30 °C, the equal-highest on record (4 other times), two of which occurred during the first ten days of the month.

The average minimum temperature was also the highest on record for Sydney Observatory Hill at 13.8 °C, 2.7 °C above the historical average. No nights dropped below 10 °C during the month for the first time on record (average 11 nights), while 10 nights exceeded 15 °C (average 2-3 nights), the equal highest on record with September 2009. The warmest night was 20.1 °C on the 10th, the earliest 20 °C night on record for Sydney.

The warmest days also featured unusually warm mornings. The 9am temperature was 25.9 °C on the 10th, the equal-warmest on record for September and the earliest such warm morning by two weeks (previous earliest was 24 September 2009). This record was later broken when temperatures reached 26.9 °C at 9am on September 26, before reaching 29.9 °C at 10 am.

See a list of September temperature records.

Other phenomena - Early season bushfires

Sydney Airport recorded an average of 8.8 hours of bright sunshine, above the historical average of 7.9 hours but not as sunny as September 2012 (9.2 hours).

The prevailing wind direction was northerly, with 33% of 3 pm winds N-W and 53% N-E, well above average for September; only 13% of 3 pm winds were southerly, half the historical average. The northwesterly winds brought warm inland air to Sydney, contributing to the record-breaking temperatures for the month.

There were eight days with strong winds observed, reaching 87 km/h at the airport and 96 km/h at Kurnell on the 26th, with gusts of 91 km/h at Port Botany on the 12th. The strong winds on the 26th caused some fallen trees and roof damage, mostly in western Sydney.

The combination of dry weather, warm temperatures and strong winds resulted in significant early-season bushfire activity during the month. Major bushfires impacted western Sydney and the Blue Mountains on the 10th, resulting in some evacuations, closed roads, and two destroyed houses. Bushfires also burnt large areas of Barrenjoey Head in the Northern Beaches on the 28th.

Extremes Records Summaries Important notes the top

Extremes Records Summaries Important notes the top

Extremes Records Summaries Important notes the top

Most values are the precipitation in the 24 hours to 9 am on the day indicated. Days marked with »» are part of a longer accumulation, which is marked like this on the final day. Values over 100 mm have been rounded to the nearest whole millimetre. Days marked with - have a rainfall report of zero; days left blank have no rainfall report (which often indicates no rain fell).
This table is very wide; you may have to scroll sideways to see all the days, and you may need to set the paper to 'landscape' to print.

Extremes Records Summaries Important notes the top