Parts of Western Australia are in for a hot weekend as heat from the interior filters into the state's southwest. Over the last week significant heat has been building over the nation's interior. Alice Springs had eight straight days with temperatures reaching 38 degrees. The hottest day was the last of the hot run when it reached 42 degrees on Wednesday. A large high pressure system over the Bight is nudging its way east. This is combining with a developing low pressure trough in the west to draw the heat over southwestern parts of WA, including Perth. Saturday will be the hotter day of the weekend with the mercury in Perth forecast to reach 35. This would make it the hottest day since April. It will be a touch cooler on Sunday with a top of 34 due to some extra cloud cover. This will make it the hottest weekend since March in Perth when the city baked through a 39 degree Saturday and a 41 degree Sunday. Relief from the heat will come for the start of the working week as a cool change gradually pushes through on Monday. Temperatures are expected to remain closer to average until at least Friday. The cool change will be accompanied by cloud cover and even the odd shower. Showers will only bring a couple of millimetres on Monday, most likely during the commute home.