Perth residents awoke to thick fog across much of the city this morning making for a gloomy start to the working week. Light winds combined with cool temperatures and high humidity to provide ideal conditions for fog formation. The fog thickened from around 7:00am bringing visibility down to 100 metres at the airport and at Pearce, in the suburbs. The fog persisted throughout the morning with visibility at the airport remaining below 300 metres at 9:00am. The fog lifted during the late morning with showers expected to develop this afternoon due to the arrival of a cold front and associated low pressure trough. The showers should be light, with less than 5 millimetres expected in Perth. Tuesday's commute should be a little brighter, as a high pressure ridge builds over the state, allowing skies to clear and some sunshine to return. The clearer skies will combine with a cold airmass in the wake of the front, however, leading to a chilly day. Both minimum and maximum temperatures will be a couple of degrees below average and fresh winds will add a wind chill factor, making it feel a few degrees colder. Minimum temperatures will cool below five degrees each morning for the remainder of the week, while daytime temperatures gradually warm. By the end of this week days will reach close to 20 degrees under mostly sunny skies.