A slow-moving low pressure system has brought unusual summer weather to WA's southwest, with some places seeing their coldest December day in over 50 years and many already receiving more than their monthly average rainfall. The low, which was fed by warm seas in the Indian Ocean, moved over the region on Saturday, bringing an end to the run of sunny and balmy weekends seen during November. Residents instead had to endure a wet and windy weekend with weather more typical of August than December enticing winter clothes from the cupboard. Perth only managed to reach 19 degrees on Saturday, 10 degrees below average and its coldest December day since 1961. Pearce also struggled to record 19 degrees, its coldest December day in 38 years of records. On top of Friday's rain, many areas experienced further showers on Saturday, with some places in the region already reaching their December average. Albany received 40mm, more than its entire monthly average in just 24 hours and its wettest December day since 1960. Further east under thunderstorms, Lake Grace collected a massive 75mm, including 11mm in just 10 minutes. As the low moves east today, showers will gradually clear the region, lingering about the southern coast until Monday or Tuesday. More typical summer weather will quickly return, as temperatures push into the 30s by late next week and into the weekend.