Much of the Sydney Basin has just experienced its warmest day since at least April and the heat will stick around for the remainder of the weekend. The mercury climbed quickly this morning, with temperatures reaching 30 degrees in the city by 10:30am. This made it the warmest day since April and with another hot day expected tomorrow this is likely to be one of the warmest weekends since January. Western suburbs of Sydney reached as high as 33 degrees in Penrith and 34 degrees in Richmond, both having their warmest days since March. Similar conditions are expected on Sunday as warm northerly winds continue to push into New South Wales ahead of a trough. Cloud will build over Sydney later though as the trough approaches, but will only bring an evening shower or two over western suburbs. Monday will bring a rainy and thundery change with as much as 10 to 20mm expected. A cooler southerly change change will push through late in the day, bringing temperatures back to the low twenties by Tuesday.