Perth failed to register any rain during the last 18 days of the month, making it the longest September dry spell in 130 years of records.
The previous September record was 17 consecutive days with no rain, set in 1987.
Luckily the first few weeks of the month were reasonably wet, gaining 44mm, only half the monthly average. But it wasn't enough to stop it becoming the driest September as a whole in six years.
The dry was experienced over much of southwest and western WA. Geraldton endured its driest September in 68 years of records, accumulating only five millimetres, 28 below average.
This comes after one of the driest winters on record, in contrast to eastern states where it was one of the wettest winters in more than a decade.
"A near-stationary high over the Bight has meant Western Australia's southwest and west coast has been in dry southeasterly or easterly winds since September 13th. No cold fronts have penetrated the region since then," Weatherzone meteorologist Brett Dutschke said.
The high finally budged during the last week of the month so winds turned relatively warm northeasterly, making the month relatively warm as a whole. The city ended up with an average maximum of 22 degrees two degrees warmer than the long-term norm, making it the warmest September since 1987 in terms of daytime temperatures. In fact, there were five days in a row of 25 degrees or warmer, one day short of the previous record of six.
It was a similar story further north. Geraldton had its warmest September in 23 years in terms of daytime temperatures. This feat was helped by a record hot 36.1 degrees on the 29th, which is 14 above the monthly average.
In contrast, Perth's nights were cold, averaging a minimum of just 8.2 degrees, one degree below the long-term norm of 9.5. This made it the coldest September in six years, in terms of overnight temperatures. A remarkable feat given that this month included the warmest September night in 51 years, 18.2 degrees, on the last night of the month. During the month there were seven nights colder than five degrees, the equalling the September record, set in 2004.
Geraldton's nights were the coldest for September in 41 years, averaging a minimum of 7.7 degrees, below the long-term norm of 9.3.
"Looking ahead to the remainder of spring and summer, the signs aren't very promising as far as rainfall goes, especially because it's traditionally a dry time of the year. Near average rainfall is likely which is not enough to make up for the deficit. For the year to date Perth is still more than 200mm short of the average," Dutschke said.
"Regarding the warmth, daytime and overnight temperatures trend to near average for the rest of spring and summer."