The onset of spring in Western Australia proved to be quite unpredictable, characterized by a variety of weather conditions throughout September. The state experienced everything from significant rainfall in the inland regions to unexpected spikes in temperature reminiscent of summer.
Photographs shared by our audience vividly depict the stark contrasts in weather across different areas of WA during this month.
The month kicked off following a notably dry winter in many regions of the state. The first substantial rainfall event did not affect Perth or the South West but instead targeted areas hundreds of kilometers inland. A sluggish trough system transported tropical moisture into the Goldfields and the Interior, resulting in extensive cloud coverage, rain, and thunderstorms in those areas.
This weather phenomenon led to precipitation levels that far exceeded the norm for locations that typically receive only 5 to 15 millimeters of rain in September. For instance, Leonora recorded a remarkable 59 millimeters of rainfall in just 24 hours by September 7, marking its wettest September day on record and nearly doubling its previous record of 32.6 millimeters set in 1984.
The intense rainfall caused road flooding around Leonora, resulting in the closure of the Goldfields Highway and the Leonora-Laverton Road.
By the end of the month, Leonora had amassed over 136 millimeters of rain, a staggering increase from its average of just 9 millimeters, and it shattered the former monthly record of 83.3 millimeters set back in 1904.
As the month progressed, a notable temperature disparity emerged across the nation. While southeastern states were experiencing cooler-than-average weather, the western regions of WA were sweltering under summer-like conditions, with daytime temperatures soaring as much as 12 degrees Celsius above the norm.
This heat wave was also influenced by the same trough system responsible for the storm activity in the interior. A robust high-pressure system to the south pushed the trough towards the southwest coast, drawing warm air from the north, which had seen temperatures reach as high as 40 degrees Celsius during the month.
The resulting northerly winds caused temperatures to soar across the southern region, with many areas setting new September temperature records. For example, Perth reached 30.3 degrees Celsius on September 16, marking its first 30-degree day of the season and the warmest day since April. This prompted many residents to flock to local beaches to enjoy the summer-like weather.
The warmth persisted into the night, with temperatures only dipping to 18.2 degrees Celsius early the following morning, just shy of the record for the warmest September minimum.
Perth was not alone in experiencing elevated nighttime temperatures; nearly a dozen locations recorded their highest minimums for September. Wongan Hills experienced a low of just 21 degrees Celsius, while Murchison set a new record with a minimum of 19.8 degrees Celsius, surpassing its previous record from 1990. Cunderdin, Beverley, and Badgingarra also exceeded their 15-year-old records.
The trend of setting new daily records continued, with Katanning hitting 31.8 degrees Celsius on September 17, just surpassing its previous record from 2006. Rocky Gully South, North Walpole, and Albany Airport also established new September temperature records, reflecting a pattern of above-average warmth.
As September drew to a close, unusual rainfall events persisted in the interior regions. Another moisture-laden system began to produce heavy rain and thunderstorms across parts of the Goldfields, Interior, and southeastern areas. Kalgoorlie-Boulder recorded over 80 millimeters of rain, approximately six times its average for September, marking yet another atypical weather occurrence for a region generally dry in spring.
This trough system eventually shifted back toward the southwest coast, evolving into a low-pressure area that brought rain to central and southern regions over the weekend. After a succession of warm, sunny days, Perth registered its coolest day of the month with a high of just 17 degrees Celsius, coinciding with the gloomy conclusion of the AFL Grand Final.
Although the city had missed much of the rainfall throughout the month, it did receive a substantial downpour on the final day, bringing its total to just over 38 millimeters—less than half of the monthly average for September.
The Bureau of Meteorology has predicted an increased likelihood of above-average rainfall across much of southern and central WA in October, which may help to compensate for the previous lack of precipitation.
