Perth is forecast to receive its first thunderstorm of summer tomorrow as a surface trough heads across the city overnight.
The Bureau of Meteorology's Neil Bennett said the storms were forecast to develop from 2am tomorrow and continue until 2pm.
Up to 5mm of rain is expected to fall on the metropolitan area during the storms.
"It's not unusual to get summer thunderstorms and this is just an example of that," he said. "We've got a surface trough of low pressure that's going to move across early tomorrow."
Mr Bennett said the thunderstorm was not forecast to include any damaging hail.
Sunny conditions are expected to return in time for the weekend and the temperature is forecast to climb from 29C on Saturday to 35C on Wednesday.
Mr Bennett said it was too early to predict the temperature during the Christmas period but pointed out Perth tended to receive one wet Christmas every eight years.
Last year Perth sweltered through 39.6C heat on Christmas Day.