The Bureau of Meteorology says most of the state is likely to have a hotter than normal summer with above average rainfall.
The bureau's seasonal outlook for December to February says there is at least a 60 per cent chance the state's western, central, southern and far north-west areas will experience above average maximum temperatures.
The outlook also predicts a high likelihood of higher than normal minimum temperatures for those areas.
The Bureau's Neil Bennett says the majority of the state also has a more than 60 per cent chance of above average rainfall.
"The major urban areas -Albany, Geraldton, Perth and Bunbury - all look as if they're more likely to see above average rainfall," he said.
"Really, it is the whole of the state except for the Kimberley, where the signal is neither one way or the other and it's really about average conditions expected.
"We do have to stress the amount of rainfall we see in those three months is typically very low anyway so it wouldn't take a huge amount of rainfall for us to see above average falls."
Mr Bennett says the outlook is largely a result of warmer than normal waters in the Indian Ocean and tropical Pacific waters.
"The forecast models were suggesting El Nino two to three months ago, but now the forecast models coming in suggest the likelihood of an El Nino has now receded," he said.
© ABC 2012
17:58 EDT With sweltering conditions expected for Sunday, but Monday will be remarkably cooler and wetter for many parts of New South Wales.