Tuesday, 2 October 2007 - Monthly Climate Summary for ACT Region - Product code IDCKGC1xx0

Dry and warm September for Canberra

Summary

  • Well below average rainfall during September
  • Warmer day and night-time temperatures 

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Rainfall

Canberra Airport recorded a total rainfall of 14.6 mm during September which is the lowest September total for 13 years (since 3.0 mm in 1994) and significantly below the historic average of 52.3 mm.  Most of the rain fell with the passage of several cold fronts through the ACT region during the month producing insignificant amounts of rainfall on those occasions.  For the rest of the month the ACT remained under the influence of a persistent high pressure system. Even though the total rainfall was well below average there were 12 rain days during September, just above the average of 10 days. There was considerable variation in September rainfall across the ACT with totals ranging from 44.4mm at Mount Ginini to 8.0 mm at Giralang.

Temperature

The mean daily temperature (the average of the mean maximum and mean minimum temperatures) at Canberra Airport was 10.3°C, slightly warmer than the long term average of 9.6°C.  The average maximum (day-time) temperature during September was 17.1 °C, slightly warmer than the long term average of 16.1°C. Canberra Airport experienced slightly warmer than average minimum (night-time) temperatures during September, the average minimum of  3.5°C being 0.3 °C above the historic average of 3.2°C.

Extremes of temperature at Canberra Airport ranged from a high of 22.1°C on the 24th to a low of −2.3°C on the 16th. Corresponding extremes for Tuggeranong ranged from a high of 22.5°C on the 25th to a low of −2.5°C on the 16th.

Other phenomena

Canberra Airport recorded 15 frosts compared to the long term average of 13 frosts. There was 1 fog (average 3 fogs).  It was generally a sunny month with sunshine averaging 8.9 hours per day (long term average 7.6 hours per day).  September recorded 4 strong wind days (average 3) but the average wind run of 223 km per day was slightly below the historic average of 225 km per day. There were no snow days (average 0).  Although no thunderstorms were recorded at Canberra Airport (average 1), there was a thunderstorm reported in Tuggeranong on the early morning of the 27th. The average air pressure of 1017.6 hPA was slightly above the long term average of 1017.4 hPa. Total evaporation of 128.6 mm was well above the long term average of 113.2 mm.

Extremes for the ACT

Hottest day
Highest temperature		 22.5°C at Tuggeranong (Isabella Plains) AWS on the 25th
Warmest days on average
Highest mean daily maximum temperature		 17.4°C at Tuggeranong (Isabella Plains) AWS
Coolest days on average
Lowest mean daily maximum temperature		 17.1°C at Canberra Airport
Coldest day
Lowest daily maximum temperature		 11.9°C at Tuggeranong (Isabella Plains) AWS on the 5th
Coldest night
Lowest temperature		 −2.5°C at Tuggeranong (Isabella Plains) AWS on the 16th
and 23rd and −5.8°C at Mt Ginini on the 4th
Coolest nights on average
Lowest mean daily minimum temperature		 2.6°C at Tuggeranong (Isabella Plains) AWS
Warmest nights on average
Highest mean daily minimum temperature		 3.5°C at Canberra Airport
Warmest night
Highest daily minimum temperature		 12.2°C at Canberra Airport on the 28th
Wettest overall
Highest total rainfall		 44.4 mm at Mt Ginini
Driest overall
Lowest total rainfall		 8.0 mm at Giralang
Wettest day
Highest daily rainfall		 10.6 mm at Tuggeranong (Isabella Plains) AWS on the 8th
Highest wind gust
 70 km/h at Canberra Airport on the 28th

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Summaries

In this table, key sites have been highlighted to make them easier to find. This table is very wide and may not fit if printed.

Summary statistics for September 2007
Maximum temperatures
for September
(°C)		 Minimum temperatures
for September
(°C)		 Rainfall
for September
(millimetres)
Mean for
September
2007		 Diff
from
normal		 Highest for
September
2007		 Mean for
September
2007		 Diff
from
normal		 Lowest for
September
2007		 Total for
September
2007		 Normal
for
September		 Rank of
September
2007		 Fraction of
September
normal
Sthn Tablelands Gburn-Monaro (district 70)
Canberra Airport

17.1

 +1.0 22.1 24th

3.5

 +0.3 −2.3 16th

14.6

52.9

 low 28%
Tuggeranong*

17.4

 −0.2 22.5 25th

2.6

 −1.5 −2.5 16th,23rd

19.0

66.5

 low 29%

*  Historic average rainfall and temperatures for Tuggeranong calculated over short period 1996−2007 only.

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Notes

This statement has been prepared based on information available at midday on Tuesday 2 October 2007. Some checks have been made on the data, but it is possible that results will change as new information becomes available.

A note about deciles: Deciles are used to give an element (in this case rainfall or temperature) a ranking. Deciles are calculated by arranging the totals in ascending order (from lowest to highest) then splitting them into 10 equal groups (thus the groups are called deciles). The first group would be in decile range one, the second group in decile range two, etc up to the highest annual totals (highest 10 per cent) being in decile range 10.

1Averages:  Historic average temperatures for Canberra Airport are based on the period 1961 to 1990 which is a convention of the World Meteorological Organisation.  Historic rainfall averages and extremes for Canberra Airport are based on all years of record 1939 - 2006. Normals are long-term averages based on observations from all available years of record, which vary from site to site. They are not shown for sites with less than 20 years of record for temperature and less than 30 years of record for rainfall, as they cannot then be calculated reliably.

Further information

Owen Offler
Climate Information Officer
Climate Services Centre
Canberra Meteorological Office
Bureau of Meteorology
Phone (02) 62470411
Email climate.act@bom.gov.au