The data is from here
maps.bonzle.com/c/a?a=f&sc=windSo the site says this is the mean windspeed at 3pm.
This site also has the calmest places in Australia.
1 Tawonga, VIC 3.9 km/h
2 Mount Beauty, VIC 3.9 km/h
3 Harden - Murrumburrah, NSW 4.4 km/h
4 Binalong, NSW 4.4 km/h
5 Timber Creek, NT 4.9 km/h
6 Eugowra, NSW 5.7 km/h
7 Canowindra, NSW 5.7 km/h
8 Corryong, VIC 6.5 km/h
9 Myrtleford, VIC 6.5 km/h
10 Toogoolawah, QLD
Not sure where most of these places are but they all must suck if you are a windsurfer. Who knows if the information is reliable or not. I don't.