Monday, 1 February 2010 - Monthly Climate Summary for Perth - Product code IDCKGC11L0
Perth in January 2010: A dry and hot month
- Second hottest January on record;
- Driest January since 2008, with Nil rainfall;
- Greatest number of warm nights in January for fifteen years with twelve.
Very dry conditions prevailed throughout the Perth Metropolitan area during January 2010. Many sites in the Perth area recorded Nil rainfall, however some stations recorded rain, mostly due to localised thundery showers on the afternoon and evening of 23 January.
Perth Metro recorded Nil rainfall in January 2010, which is the driest January since 2008 (Perth has recorded Nil rainfall in January on thirteen other occasions). Perth Metro last recorded rainfall in the 24 hours to 9 am on 20 November 2009 with 0.6 mm. The current dry spell of 73 days to 9am on 1 February is Perth's second longest dry spell on record, the longest being 83 days between 15 December 1974 and 7 March 1975.
Maximum temperatures were very much above average throughout the Perth Metropolitan area. Heatwave conditions prevailed over the city between 17 and 19 January, with unusually high daily maximum temperatures observed at a number of sites. Perth Metro recorded three days of maximum temperatures above 41.0 °C which has happened on only two other occassions (13 to 15 March 1922 and 7 to 9 February 1933). The highest daily maximum temperature during the heatwave period, and for the month, was at Pearce RAAF which recorded 44.1°C on the 18th.
Perth Metro's mean daily maximum temperature in January was 33.4°C, which is well above average and ranked as the second hottest mean maximum temperature for January on record. The highest for January was 34.4°C in 1962. Daily maxima ranged from a mild 23.9°C on the 11th to a very hot 42.9°C on the 17th, which was Perth's highest daily maximum temperature for January since the record of 45.8°C on 31 January 1991.
Minimum temperatures were generally above average for the Perth area in January 2010. Warm to hot overnight minimum temperatures were experienced throughout the Perth Metropolitan area on the 18th and 19th January. Jandakot Aero broke its highest daily minimum temperature record, observing 27.1°C on the 19th. The highest overnight minimum temperature during January 2010 was at Pearce RAAF with 28.8°C on the 18th.
Perth Metro's mean daily minimum temperature in January was 18.9°C, above the long-term average of 17.8°C. Daily minima ranged from a mild 14.0°C on the 1st to a hot 26.8°C on the 19th, which is the highest daily minimum temperature for January since the record of 27.8°C on 21st January 1989.
Perth recorded 12 warm nights during January 2010 (a warm night in Perth is when the overnight minimum temperature is 20°C or higher), which was equal to the record set in January 1995. The average for January is six.
About 60-70% of mornings experienced east to southeasterly winds for all the metropolitan mainland sites, which is close to the long term average. Sites along the hills experienced fewer afternoon sea breezes than normal and Perth Airport had southwest to westerly winds approximately 10% less frequent than normal.
The windiest day around the city was on the 30th, with an enhanced seabreeze causing wind gusts of 89 km/hr at Rottnest, 76 km/hr at Garden Island and 69 km/hr at Swanbourne.
Perth received 12.4 hours of sunshine per day on average in January 2010 compared to the long term normal of 11.6 hours. This is the third highest amount of sunshine hours for January on record behind 1974 (12.6 hours) and 1984 (12.5 hours).
|Extremes in January 2010|
44.2 °C at Pearce RAAF on the 18th|
|Warmest days on average||
36.0 °C at Pearce RAAF|
|Coolest days on average||
27.2 °C at Rottnest Island|
21.5 °C at Garden Island HSF on the 11th|
9.8 °C at Jandakot Aero on the 11th|
|Coolest nights on average||
16.0 °C at Bickley|
|Warmest nights on average||
19.5 °C at Champion Lakes|
19.5 °C at Gosnells City
19.5 °C at Rottnest Island
28.8 °C at Pearce RAAF on the 18th|
6.2 mm at Jarrahdale|
4.0 mm at Gosnells City on the 24th|
|Highest wind gust||
89 km/h at Rottnest Island on the 30th|
|Record highest January mean daily maximum temperature|
Mean daily maximum
for January 2010 (°C)
|Medina Research Centre||33.5||32.3||in 2008||21||30.3|
|Record highest January daily minimum temperature|
Highest daily minimum
in January 2010 (°C)
|Jandakot Aero||27.1||on the 19th||26.4||on the 27th in 1999||20||16.4|
|Summary statistics for January 2010|
|Garden Island HSF||28.9||+2.4||40.4||17th||19.1||+0.6||14.8||1st||0.4||9.1||average||4%|
|Medina Research Centre||33.5||+3.2||43.8||17th||18.2||+1.5||12.3||11th||0||11.0||lowest||0%|
|Perth Metro*||33.4||+2.8||42.9||17th||18.9||+1.1||14.0||1st||0||9.5||v low||0%|
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.
|Garden Island HSF||-||-||-||-||-||-||-||-||-||-||-||-||-||-||-||-||-||-||-||-||-||-||-||0.4||-||-||-||-||-||-||-|
|Medina Research Centre||-||-||-||-||-||-||-||-||-||-||-||-||-||-||-||-||-||-||-||-||-||-||-||-||-||-||-||-||-||-|
A Monthly Climate Summary is prepared to list the main features of the weather in Perth 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 1 pm on Monday 1 February 2010. 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 5 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
(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.
*Official Perth observations have been recorded at several different sites with varying instrumentation over the years, and these changes can affect the continuity of the climate record. For the current Mt Lawley site, the most significant changes of this kind relate to temperature and rain days.
For that reason, current mean temperature and rain-day data quoted here are based only on readings from the Mt Lawley site, which commenced observations in 1993. Sunshine recordings are from Perth Airport and for similar reasons current means use only Perth Airport data, which commenced in 1993.