Sydney is blessed with wonderful weather, even in winter the temperature rarely falls below 10C.

Spring is absolutely gorgeous in Sydney, The average temperature ranges from  13 (55)F at night to 22(72F) in the day. The weather is cool but are usually very pleasant and sunny. Spring is usually Sydney's driest season, the 2000 Olympic Games were held mid September for this reason! Spring starts September 1st - Nov 30th.

Autumn is lovely with sunny clear days. Autumns starts on March 1 and ends 31st May.

Winter in Sydney can be chilly with strong westerly winds.  Winter starts from June 1 to August 31.

Summer in Sydney is what all Sydneysiders love. It's truly beach weather, so slap on the sunscreen and head to one of the wonderful beaches. Summer starts in December 1st - February 28th.

Swimming and Water Temperature

The Australian east coast is influenced by the East Australian Current which brings warm water down the coast from the Coral Sea.  Its effects vary from year to year but are strongest in summer and weakest in winter.   Summer water temperatures around Sydney are generally around 22 degrees C.  The water is usually most comfortable for swimming between Christmas (25 December) and Late April or early May.  Earlier in December the air temperature is lovely, but the water is colder. As autumn progresses the air temperature is cooler and the water still warm. 

Rainfall and Coastal / Inland variations

Australia gets pretty regular droughts. You'll also see from the tables below, in Sydney they get as much or even more rain in summer than in the winter months.  Winter can be cool or cold (to local sensibilities) but have clear blue skies.  In a protected position out of the wind it can be very pleasant indeed.  If they are lucky enough to get some rain, it can make summer quite sticky and humid, but this is no problem if you're enjoying pursuits by the water.

The coastal suburbs and beaches get double the rain that you get further inland.  You might find it's pouring rain in central Sydney or at the beach, but clear at Parramatta if you're thinking of heading out that way. Most of the time in summer rainfall comes as thunderstorms after a hot day and passes quickly.   If you really want to avoid rain and you've got a car, get yourself out to a water catchment area they don't seem to get much rain at all!!

Inland areas also get hotter and colder than the coast, with more days over 40deg.  In winter the temperature is frequently down to freezing point and frosts are common.  Summer nights inland are also cooler than they are by the coast.  In the Mountains winter is of course colder still, but cooler than the coast in summer, so bear these variations in mind when day tripping or if you're in the western areas for a sunrise balloon flight or something like that.  For "inland" read Parramatta and anywhere as far west as that eg Richmond, Windsor, Camden areas.

Which time to go?

All seasons are wonderful but a favourite time in Sydney is summer and spring. On the other hand, if you're not so much into the beach culture autumn and winter are good - in Autumn you can still swim, it's more comfortable for bush walks and other active pursuits away from the water. So you see there's a season for everyone. 

The most popular holiday times for Australians in the south are Christmas - January and April school holidays, especially over the Easter weekend.  This can make advance planning a good idea at these times if you're heading to satellite areas around Sydney overnight.  It's a good time to be in Sydney itself, because many of the locals have buzzed off on holidays, so public transport and roads are not as busy.  If you have kids, school holidays has the benefit of offering additional activities for kids at museums and zoos and in the National Parks (see the Travelling with kids page).

Note: For travellers who don't cope well with temps in the summer over 25 degrees C, avoid Australia between Oct-Mar. Temps over 30 degrees C between Oct - Mar can be stifling for those who are not used to hot summers. It should be noted temps around 20 degrees C in the winter in Australia is not unusual and makes for ideal sightseeing conditions.

Trying to decide a time for a trip to both The Great Barrier Reef and Sydney?

If you're trying to balance a trip that takes in different areas of Australia, you'll need to be balancing the weather in the different areas and this will generally involve a compromise, especially if you want to take in The Great Barrier Reef  as well as the southern Capitals.  Sydney beaches are at their best when Far North Queensland (FNQ)  isn't unfortunately. No getting around it.  The main thing you'll need to decide is whether you want to surf. You can do this in Sydney but not FNQ.

Note: The best time of year for the Reef is the southern winter up to September.  After that you start getting into the hot, wet season.  So best time if you are visiting Sydney and the Reef would be September / October.

 http://www.bom.gov.au/cgi-bin/wrap_fw...

http://www.bom.gov.au/

http://www.eldersweather.com.au/nsw/s...