Temperatures dropped to their coldest for the year last night as Perth is set to shiver through a run of cool nights. The mercury cooled to three degrees last night, six below average and the coldest since July last year. Nearby, Jandakot stayed just above freezing at one degree the coldest night in June since 2012. Freezing temperatures are not unheard of in Perth as it does drop below zero once or twice a decade. The cool night was caused by a cool air mass left in the wake of a cold front combined with clear skies and light winds under a building ridge of high pressure. The high pressure system and cold air mass are set to linger over the state's capital for the next few days, with nights looking to remain cold until the beginning of next week. The good news is the clear skies and light winds will bring beautiful winter days with daytime temperatures to warm close to the 20s. A cold front will arrive on Tuesday bringing gusty showers and an end to the cool nights.