Hi Adrian,
First clue - weather map. Bookmark
http://www.bom.gov.au/australia/char...ptic_col.shtml because seeing is usually best when there is a big, fat high pressure system - labelled "H" - smack over Sydney. This is why Saturday night will be hopeless, but by Monday or Tuesday that H currently west of Perth will be over Sydney.
Second clue: Isobars (lines on this map) close together = lots of wind = poor seeing. Isobars far apart = calm, and (maybe) good seeing. A cold front (curve with pointy bits) means seeing will be utter crap.
Third clue: Sources of heat nearby:
a) domestic houses with dark tile roofs - these get hot in the sun. They spend all night cooling... by creating thermals that destroy your seeing.
b) nearby buildings get very hot in full sun (summer) and spend all night producing thermals to cool down. if you have lots of big-box buildings nearby its basically a catastrophe seeing-wise.
c) in winter, thanks to air-conditioning systems, buildings are still warm and spend all night creating thermals as the cool down, not not as badly as summer.
And guess what is near you...
Fourth clue - large areas of tarmac. its black, it gets hot in the sun, and you know what that means - more thermals. And guess what is right near you...
And thats before thinking about whether you are looking through jet exhaust.
Fifth clue: local terrain and microclimate. The seeing you will experience is most affected by the first 1000 metres of air immediately above you - and in particular what lies upwind of you. If the local airflow over your site is turbulent you will have bad seeing, period. For a frequent chance at good seeing you have to find a site which has a prevailing breeze with laminar flow over the top. I only know of 2 such locations; one being the NSAS site at Terrey Hills, the other being Shipley Plateau west of Blackheath.
Best way I can describe this is to imagine your locality reduced in scale to the size of a desktop, then imagine the air as being like a river of water flowing over that. If it would flow smoothly, great. if its turbulent, poor seeing.