I've lived in WA for a couple years now and have noticed that on the really hot days when the temperature gets over 36 or 37 degrees, the seabreeze is always much lighter...
Often the wind will be forecast for a good strong seabreeze on these days, but rarely does the wind get over 10-14 knots.
Does anyone know the reason why these really hot days have this effect on the wind? The basic principals of a seabreeze would suggest that the hotter the day, the stronger the seabreeze, but clearly this isn't the case.
It is because of the gradient breeze fighting the sea breeze.
The extra hot days normally has a northerly gradient, bringing with it the heat from the desert and the north.
When the gradient is in direct competition of the South West sea breeze it will be a lighter day.
If the breeze swings through the north it will be light, but if it swings through the south it will be stronger(bringing cooler southerly breeze help the temp difference between the land and the sea).
If you get the hang of reading synoptics (you can see the current one by clicking on the 7 day forecast), you'll see troughs forming.
Good thing about a trough is it usually fangs when they move inland. 
WA weather patterns / synoptics explained here:
www.seabreeze.com.au/info/wind.asp
