A month's worth of rain caused flash flooding in Adelaide last night, with other parts of the state picking up their heaviest falls in half a decade. A line of thunderstorms formed over the eastern Eyre Peninsula on Thursday afternoon before intensifying rapidly over Spencer Gulf. More moisture was pumped into the storms as they crossed Gulf St Vincent, before hitting Adelaide with full force around 5pm local time. Rounds of heavy rain and thunder lashed Adelaide for two hours, delivering 20mm to the city. At times rain rates reached close to 10mm in 10 minutes, which was enough to produce flash flooding during the peak hour commute. Showers continued on and off overnight bringing the city's total to 30mm by this morning, which is half the monthly average for September. Burnside collected 51mm, just 3mm shy of the monthly average and a new daily record for this time of year. Rain and storms had a similar impact on other parts of the state. In the Lower South East, Naracoorte had the heaviest rain in five years with 56mm in the last 24 hours. Mt Gambier received 53mm, the heaviest September rain on record. Showers and isolated thunderstorms will continue in the state's south and east this morning in the wake of the cold front and low pressure system that triggered last night's deluge. Conditions will improve this afternoon, with calmer weather returning for the weekend. It will be dry when Adelaide take on North Melbourne at Adelaide Oval on Saturday night.