ACT in September 2011: Hot days and cold nights in Canberra

  • Below average rain.
  • 4th warmest September on record for maximum temperatures.
  • Below average minimums, coolest since 1994.
  • 3rd warmest September day on record, and 5th coolest September night.

Rainfall

Canberra Airport recorded 32.6 mm of rain during September, below the historical average of 52 mm. The rain fell over 9 days, close to average for September, with a maximum daily fall of 10.2 mm on the 29th, reaching 25.2 mm at Mt Ginini on the same day. Rain exceeding 5 mm was also recorded on the 7th and 25th of the month, with clear conditions dominating the rest of September.

Temperature

Maximum temperatures were very warm during September at 18.2 °C, 2.0 °C above the historical average of 16.2 °C. This was the 4th warmest September on record for maximum temperatures, and the warmest since September 2006 (19.4 °C). The warm days were associated with generally clear conditions and above average sunshine during the month. Temperatures were particularly warm between the 17th and 19th when temperatures exceeded 24 °C for three consecutive days, peaking at 27.1 °C on the 19th, the 3rd warmest September day on record. Temperatures again reached 25.3 °C on the 23rd, with the second highest number of days above 24 °C on record for September following five days in 1987. The coolest temperature during the month was 12.6 °C, only exceeded during September 2007 when no days dropped below 12.7 °C.

In comparison, the average minimum temperature during September was 1.9 °C, 1.4 °C below the historical average of 3.3 °C. This was the coolest September since 1994, associated with the generally clear conditions during the month. Only one night during September exceeded 10 °C, with 13 nights below 0 °C and 7 below -2 °C, double the historical average and the most -2 °C nights since 1971. Temperatures were particularly low between the 10th and 14th, with five consecutive nights below -1 °C, the longest cold spell on record for September. The minimum temperature was just -5.2 °C on the 10th, the 5th coldest September night on record and the coldest since -6.4 °C on September 10 1982.

The mean daily temperature was 10.1 °C, 0.3 °C above the historical average.

Wind

Winds were generally northwesterly during September, with 75% of 3pm winds between WNW and NNW, normal for September. No strong wind days were reported at the Airport during the month, with a maximum wind gust of 83 km/hr on the 19th. The strongest wind gust anywhere in the ACT was 107 km/hr at Mt Ginini on the 20th.

Other phenomena

Canberra Airport reported 7.9 hours of sunshine during September, slightly above the historical average of 7.7 hours. There were no thunderstorms reported at the Airport, with five reported in the ACT. Six frost days were reported during the month, below the September average of 13 frosts.

Further information

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Extremes in September 2011
Hottest day 27.1 °C at Canberra Airport on the 19th
Warmest days on average 18.2 °C at Canberra Airport
Coolest days on average 7.9 °C at Mount Ginini AWS
Coldest day 0.1 °C at Mount Ginini AWS on the 30th
Coldest night -6.6 °C at Mount Ginini AWS on the 10th
Coolest nights on average -0.2 °C at Mount Ginini AWS
Warmest nights on average 2.7 °C at Tuggeranong (Isabella Plains) AWS
Warmest night 12.8 °C at Canberra Airport on the 20th
12.8 °C at Tuggeranong (Isabella Plains) AWS on the 20th
Warmest on average overall 10.3 °C at Tuggeranong (Isabella Plains) AWS
Coolest on average overall 3.9 °C at Mount Ginini AWS
Wettest overall 75.2 mm at Mount Ginini AWS
Wettest day 25.2 mm at Mount Ginini AWS on the 29th
Highest wind gust 107 km/h at Mount Ginini AWS on the 20th

Summary statistics for September 2011
Maximum temperatures
for September
(°C)
Minimum temperatures
for September
(°C)
Rainfall
for September
(millimetres)
Mean for
September
2011
Diff
from
average
Highest for
September
2011
Mean for
September
2011
Diff
from
average
Lowest for
September
2011
Total for
September
2011
Average
for
September
Rank of
September
2011
Fraction of
September
average
Canberra Airport 18.2 +2.0 27.1 19th 1.9 -1.4 -5.2 10th 32.6 52.0 low 63%
Mount Ginini AWS 7.9   17.3 19th -0.2   -6.6 10th 75.2
Tuggeranong (Isabella Plains) AWS 17.9   26.0 19th 2.7   -4.0 10th 40.4

Notes

As of March 2010, the official station for Canberra is 70351 'Canberra Airport'. Averages from the previous site, 70014 Canberra Airport Comparison, are used for comparisons (all years of record).

A Monthly Climate Summary is prepared to list the main features of the weather in ACT Monthly Summary using the most timely and accurate information available on the date of publication; it will generally not be updated. Later information, including data that has had greater opportunity for quality control, will be presented in the Monthly Weather Review, usually published in the fourth week of the month.

This statement has been prepared based on information available at 9 am on Tuesday 4 October 2011. Some checks have been made on the data, but it is possible that results will change as new information becomes available.

Averages are long-term means based on observations from all available years of record, which vary widely from site to site. They are not shown for sites with less than 20 years of record, as they cannot then be calculated reliably.
The median is sometimes more representative than the mean of long-term average rain.

The Rank indicates how rainfall this time compares with the climate record for the site, based on the decile ranking (very low rainfall is in decile 1, low in decile 2 or 3, average in decile 4 to 7, high in decile 8 or 9 and very high is in decile 10).
The Fraction of average shows how much rain has fallen this time as a percentage of the long-term mean.

Further information

Media
(03) 9669 4057
Enquiries