After speaking to the Bureau of Meteorology's manager of climate prediction services and its severe weather forecaster, Michael Logan, it seems only one thing is certain: it's going to be a bit of a roller-coaster and we are in for a lot of varied weather.

Don't rule out some very hot days, thunderstorms with the possibility of high winds and severe hailstorms - and the bushfire risk is likely to be increased.

Add to that the expectation that there is a 70 per cent chance of receiving above-average rainfall over the summer months and, it seems, anything goes.

Saturday's predicted top of 36 degrees for the city centre was clouded out, but the mercury still pushed above 30, and all the way to 40 in Penrith. On Sunday, it is forecast to drop to 25. ''It is a big drop,'' said Julie Lewis, a meteorologist from the bureau. But the accompanying humidity is expected to stick around until a change on Tuesday.

The long-term outlook is for a ''typical'' Sydney summer, with more hot days than the past two summers, which were moderated by the La Nina effect.

Mr Logan said: ''Thunderstorms are likely to involve more wind and more hail than the past two seasons have given us.''

And he didn't rule out a damaging hailstorm like the ones that hit Sydney in 1999 and 2007.

''It's not to say that we will get something like that but people need to have it in the back of their minds that hailstorms do occur in Sydney and it's only a matter of time until we get another one,'' he said.

''The last couple of summers there hasn't really been any bushfire threat in Sydney. Coming out of two very wet years, people just need to remember what sort of bushfire risk is around.''

with James Robertson