Wednesday, 1 August 2007 - Monthly Climate Summary for Canberra Averages Summary - Product code IDCKGC17L0

Dry July with near average temperatures in Canberra

Summary

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Rainfall

Canberra Airport recorded a total rainfall of 19.8 mm during July, well below the historic average of 41.3 mm. Most of the rainfall occurred during the period 2nd to the 8th with the passage of several cold fronts through the ACT region.  The remainder of the month remained relatively dry with the ACT under the influence of a persistent high pressure system.  However, on the 26 and 27 July an upper level trough passed through the region producing some thunderstorm and shower activity, with reports of pea size hail in the northern and southern suburbs of Canberra on the 27th. There were 16 rain days during July, well above the average of 10 days. There was considerable variation in July rainfall totals across the ACT with totals ranging from 107.6 mm at Corin Dam to 17.4 mm at Tralee.

Temperatures

The mean daily temperature (the average of the  mean maximum and  mean minimum temperatures) at Canberra Airport was 6.0°C which is 0.4°C warmer than the historic average of 5.6°C.  The average maximum (day-time) temperatures during July was 11.3°C which is exactly the same as the long term average.  However, Canberra Airport experienced slightly above average minimum temperatures during July, the average minimum of 0.6°C being 0.7°C above the historic average of −0.1°C.  However, there were considerably colder nights in Tuggeranong where the average minimum temperature was −0.3 °C.

Extremes of temperature at Canberra Airport ranged from a high of 15.7°C on the 26th to a low of −4.7°C on the 17th. Corresponding extremes for Tuggeranong ranged from a high of 16.7°C on the 26th to a low of −6.8°C on the 17th.

Even though the nights were milder overall there were still 21 frosts recorded during July ( average of 21 frosts). There were 7 fogs (average 7 fogs).  It was generally a sunny month with sunshine averaging 6.3 hours per day (long term average 5.7 hours per day).  July was windier than usual with an average wind run of 201 km per day compared to the long term average of 182 km per day. There were 2 strong wind days (average 2). There were no snow days (average 0) reported at Canberra Airport during July, however there was snow on the hills surrounding Canberra on the 17th. There was 1 thunderstorm (average 0) on the 27th associated with  the passage of an upper level trough. Even though there was no hail days reported at Canberra Airport several northern and southern suburbs reported pea size hail on the 27th. The average air pressure of 1020.0 hPA was close to the long term average of 1020.6 hPa. Evaporation was 51.6 mm close to the average of 51.7 mm. 

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.