The thunderstorms will be coupled with evening temperatures in the low 20s, higher than Sydney's December average minimum of 17.6 degrees, creating the "most humid period of the season," Mr Dutschke said.

Melbourne, Hobart and Adelaide are also likely to have a wet week, with maximum temperatures in the low to mid-20s forecast in all three cities.

In Perth, the Indian and Australian cricket teams and spectators are set to sweat through the first day of the second Test, with a forecast 38-degree day on Friday.

In Queensland, Cyclone Owen is expected to be upgraded to category three later this week, having previously been downgraded from cyclonic levels.

The so-called "zombie cyclone" started last week near the Solomon Islands and reached category one on Monday, then was downgraded before it re-strengthened to its current category one status.

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"If anything, it [Cyclone Owen] is earlier than normal, but it is still within the wet season," the Bureau of Meteorology’s Annabelle Ford said.

Bureau of Meteorology State Manager for Queensland, Bruce Gunn urged the public to stay tuned for updated warnings.

"With many people travelling during the school holidays ... stay tuned for updated warnings, be aware of local conditions and always follow the advice of local emergency services," he said.