Parts of Western Australia have been baking in the sun this week, a hot sun for April. The heat peaked on Thursday with temperatures rising to the mid 30s, as much as 13 degrees above average and more typical of summer. Thursday was the hottest April day in more than a decade for parts of the state's southwest, including Perth. Perth, Perth Airport, Gooseberry Hill, Albany, Dwellingup and Rocky Gully all had their hottest April day since 2001. For Perth, its maximum of 36.2 degrees, making it the equal hottest April day in 42 years. On the same day in April 2001 it also reached 36.2 degrees in the city. The heat has been due to a weaker-than-normal monsoon to the north and a lack of cold fronts to the south, enabling clearer-than-normal skies, hence a build-up of heat. In contrast West Roebuck in the north could only manage a top of 25 degrees by 5pm, 10 degrees below average. If the Kimberley town stays cooler than 25.3 degrees overnight, this will be its coolest April day in at least 14 years. Sun-shielding cloud streamed across the region, a result of a strong jetstream interacting with a trough off the coast. For the southwest of the state, a cooler wind change is making its way through, in the form of a weak front. The front will only manage to bring the odd light shower to the far southwest overnight but will bring noticeable cooling. This will bring an end to Perth's late-season-five-day spell of 30 degrees. It is only the 13th time Perth has strung five 30-degree days together this late in autumn in 130 years of records. Some heat will return early next week but only three days are likely to reach 30 degrees in Perth.