Tuesday, 1 July 2008 - Monthly Climate Summary for Sydney - Product code IDCKGC15x0

Cloudiest start to winter since 1945

Summary

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  • Close to average rainfall on coast, above average rainfall western suburbs
  • Mild days - above average daytime temperatures
  • Very mild nights - highest average minimum temperature since 1967 (2nd highest on record)
  • Cloudy month - below average sunshine hours
  • Cloudiest start to winter (1−15th June) since 1945

Rainfall

There was close to average rainfall over coastal Sydney during June while the western suburbs had above average falls. At Observatory Hill the total of 127.2 mm was only a few millimetres below the historic June average1 of 130.6 mm. There were 14 rain days during June which is a little above the June average of 11 days. Most of Sydney's rain fell during the first half of the month, caused mainly by low pressure systems off the NSW coast and moist onshore winds. The last week or so was sunny, dry and stable with the persistence of high pressure systems over NSW.

The wettest suburbs were on the north shore where Turramurra North recorded 216.8 mm. The far SW suburbs recorded the lowest totals with only 53.0 mm at Camden Valley Golf Resort.

Light to moderate rainfall was recorded over the Warragamba Dam catchment during June. In the lower catchment monthly totals were around 70−90 mm but in the upper catchment (near Goulburn) only 30−40 mm was recorded. This contributed towards a slight increase in storage levels during June. Recent rainfall in Sydney's drinking water catchments can be found on the Sydney Catchment Authority web site http://www.sca.nsw.gov.au/dams/rainfall.html.

Temperatures

June was a mild month across the Sydney basin with both the maximum and minimum temperatures significantly above the historic averages. The average maximum temperature at Observatory Hill of 18.6°C was 1.7°C above the historic June average1 . This is the 10th highest in 150 years of record. Slightly above average maximum temperatures were recorded at all sites across the Sydney metropolitan area. Sunny days during the last week or so of June and the lack of any significant cold changes throughout the month contributed towards the mild daytime temperatures.

Sydney's nights were very mild during June, especially during the first 3 weeks of the month with the return of cold nights only during the final week. The average minimum temperature at Sydney Observatory Hill was 11.9°C which is 2.7°C above the historic June average 1. This is the highest average minimum temperature for June since 1967 (when 12.5°C) and the 2nd highest in 150 years of record. The western suburbs experienced cooler nights but were still well above the historic June average and at many places the 2nd highest on record for June. Sydney Airport recorded its highest average June minimum on record (see table below). The mild nights during the first 3 weeks of June were caused partly by prevailing SE-NE winds, high humidity and persistent cloudy skies. Cold nights returned to Sydney only when high pressure systems became established over NSW during the last week or so and SW winds introduced colder, drier air.

Some sites had their highest June mean daily minimum temperature on record.

Wind

Sydney experienced a dominance of winds from between the west and south during the afternoons with around 60% of all winds from this direction, compared to the normal frequency of about 50%. The highest wind gust in the greater Sydney area was 72 km/hr at Sydney Airport on 3 separate days, 13th, 14th and 26th. However, the more exposed coastal site at Wattamolla in the Royal National Park south of Sydney, recorded winds up to 96 km/hr on the 15th.

Other phenomena

Cloudy conditions prevailed during the first half of June with very little sunshine - the cloudiest start to winter since 1945 (based on period 1−15 June). However, the final week saw the return of clear, sunny days. The average sunshine for the month was 4.7 hours per day (equal third lowest). Normally Sydney would expect an average of around 6.0 hours of sunshine per day.

The first half of the month saw high humidity in Sydney associated with prevailing onshore winds. This contrasted sharply with the last week or so with the return to low humidity associated with westerly winds. The averge humidity at 9am was 78%, the highest since 1989. Fogs were recorded on the 10th and 12th with visibility reduced to 400 metres at the airport. No thunderstorms occurred in Sydney during June although lightning was reported out to sea on the 13th.

Further information

NSW Climate Services Centre
Bureau of Meteorology
Phone (02) 9296 1555
Email reqnsw@bom.gov.au

Extremes for the Sydney area

Hottest day
Highest temperature		 22.7°C at Richmond RAAF on the 11th
Warmest days on average
Highest mean daily maximum temperature		 18.8°C at Liverpool
Coolest days on average
Lowest mean daily maximum temperature		 16.9°C at Springwood
Coldest day
Lowest daily maximum temperature		 13.7°C at Terrey Hills AWS on the 14th
Coldest night
Lowest temperature		−2.4°C at Camden Airport AWS on the 30th
Coolest nights on average
Lowest mean daily minimum temperature		 7.6°C at Badgerys Creek AWS and Camden Airport AWS
Warmest nights on average
Highest mean daily minimum temperature		 11.9°C at Sydney (Observatory Hill)
Warmest night
Highest daily minimum temperature		 15.5°C at Sydney Airport on the 4th
Wettest overall
Highest total rainfall		 216.8 mm at North Turramurra
Driest overall
Lowest total rainfall		 53.0 mm at Camden Valley Golf Resort
Wettest day
Highest daily rainfall		 85.2 mm at North Turramurra on the 5th
Highest wind gust
 72 km/h at Sydney Airport on the 13th, 14th and 26th

AWS = Automatic Weather Station

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Records for the Sydney area

Record highest June mean daily minimum temperature
Mean daily minimum
temperature
for June 2008 (°C)		 Previous highest
for June		 Years of
record		 Normal for
June
Sydney Airport
11.6
11.5
in 1991 and 1967
70
8.5

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Summaries for the Sydney area

This table is very wide and may not fit if printed.

Summary statistics for June 2008
Maximum temperatures
for June
(°C)		 Minimum temperatures
for June
(°C)		 Rainfall
for June
(millimetres)
Mean for
June
2008		 Diff
from
normal		 Highest for
June
2008		 Mean for
June
2008		 Diff
from
normal		 Lowest for
June
2008		 Total for
June
2008		 Normal
for
June		 Rank of
June
2008		 Fraction of
June
normal
Sydney (Observatory Hill) 18.6 +1.7 22.1 12th and 30th 11.9 +2.6 7.9 28th and 29th 127.2 130.6 normal 97%
Bankstown Airport 18.4 +0.7 21.0 12th 9.0 +2.3 2.4 26th 85.0 75.4 high 113%
Camden Airport 18.3 +0.6 21.2 19th 7.6 +3.1 −2.4 30th 82.2 59.0 high 139%
Liverpool 18.8 +0.9 22.1 12th 8.5 +2.3 −0.3 30th 81.8 71.3 high 115%
Parramatta 18.4 +0.6 21.6 13th 9.4 +2.0 4.6 23rd 101.2 84.2 high 120%
Prospect Reservoir 18.0 +0.7 20.7 19th 9.7 +2.3 3.3 28th 102.0 75.1 high 136%
Richmond RAAF 18.4 +0.8 22.7 11th 7.7 +2.6 −0.5 27th 86.2 56.4 high 153%
Springwood* 16.9   21.2 11th 9.5   4.9 29th 103.6 77.4 high 134%
Terrey Hills* 17.1   20.7 12th 10.3   6.1 23rd 120.4

* new stations, no historic average temperatures available and no historic average rainfall available for Terrey Hills

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Notes

This statement has been prepared based on information available at 10am on Tuesday 1 July 2008. Some checks have been made on the data, but it is possible that results will change as new information becomes available.

1Averages:  historic rainfall and temperature averages are based on all available data.  

Normals 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 10 years of record, as they cannot then be calculated reliably.
The median is sometimes more representative than the mean of "normal" 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, normal in decile 4 to 7, high in decile 8 or 9 and very high is in decile 10).
The Fraction of normal shows how much rain has fallen this time as a percentage of the long-term mean.

Further information

NSW Climate Services Centre
Bureau of Meteorology
Phone (02) 9296 1555
Email mikede@bom.gov.au