The 'Bridgewater Jerry' is a fog which occasionally affects the Bridgewater–Hobart area. At night, in cooler months, cold air drains down the mountains of southern Tasmania as katabatic winds and collects in the Derwent Valley. Fog will form if this invading air is moist and cool enough. It drains out of the valley in the mornings, blowing the fog with it. The fog mainly affects the Derwent and the northern and western suburbs of Hobart, but occasionally reaches the Eastern Shore.
The most likely explanation of the term 'jerry' is that it came with convicts from London, where it was thieves' slang for 'fog' or 'mist'. In 1821 Governor Macquarie, staying at Austins Ferry, could not leave for Hobart until 12.30 pm due to thick fog – probably the first recorded Bridgewater Jerry.