Residents of Western Australia's southwest can be excused for dreaming of summer or Neil Diamond last night and kicking off the blankets. Perth is one of many centres in the southwest which have just broken heat records. The capital has just had its warmest August night in more than 100 years of records. Its overnight minimum temperature of 17.1 degrees is 10 degrees above the August average and is only two degrees short of the average maximum for this time of year - "Hot August Night" as Neil Diamond would sing. Nights usually aren't this hot until at least October when spring has well and truly shaken off winter. It is more typical of a December night. High humidity has been one major contributor. Humidity has been hovering around 80 percent, well above the normal 55 percent for this time of year. This humidity has come about with the aid of warmer-than-normal seas off the Perth coast. The warmer seas have provided a near-stationary low pressure trough with the fuel for generating cloud and rain, leading to warm summer-like nights. The effects have also been felt further inland, where Pearce and Brookton had their warmest August night in more than 40 years of records. It was the second warmest August night in 70 years of records at Perth Airport, just 0.1 of a degree short of the record 16.7 degrees. Looking at rainfall, not much has fallen in Perth itself yet, although it is getting heavier and 20-to-40 millimetres is likely by tomorrow morning, after another fairly warm night. Amongst the wetter places in the last 24 hours were Bridgetown and Jarrahwood, just south of Perth, with more than 40mm each. This is a four-year high for Bridgetown. Donnybrook picked up another 35mm to add to its 51mm the previous day. This makes it the wettest two-day spell in 10 years and wettest two days in August in 36 years. The band of the heaviest rain will edge north, through Perth overnight and reach the Central West tomorrow before dissipating over land on Thursday night ahead of a colder, drier change. Nights will then return to more typical August-like nights, within a few degrees of average. Once another cold change moves through this weekend, southwest WA can even expect some frost as temperatures drop by more than 10 degrees. Perth should cool to about six degrees early Monday morning.