Nullabor winds

It can/will change as each new front comes through.
Watch here....
Windy.com
Last year we came across the Nullarbor 3 times. On the last occasion we stopped in Noresman for 3 nights waiting for the weather system and a few nights west of Fowlers Bay and managed a good tail wind all the way from Wiluna to Adelaide.
Cheers,
Peter
OKA196 motorhome

We have crossed the Nullarbor 14 times with the van on, and at differing times, but mainly Spring and Autumn. We have encountered all weather types, and most have had winds from the front quarter and side. You can plan for it, but I have found to just go for it to fit your itinerary, although you may need to take more notice of the weather if you want to camp along the Bunda cliffs, or fly your drone over the cliff face (and count on getting it back). Regardless, a good trip to be had.
Cheers...

Currently because of the constant high pressure in the Bight and the lows over the far north the winds are tending to be from the east

How long is a piece of string type question, but assuming you're asking because you're towing, tuck yourself up behind any number of very large trucking units... Downside is you'll miss the amazing landscape mosaic.

It doesn't matter which time of the year you travel across the Nullarbor, or anywhere for that matter when you are towing. It is always a headwind, and also always uphill!

My wife and I waited in Geraldton for 3 weeks once because the weather down South was dreadful. Eventually, we had to move on, and by chance had a savage tailwind as we crossed. We stopped at Penola, and next morning I heard on the local ABC that the winds were 85 km/h, gusting to over 110 km/h. I had awesome fuel consumption that crossing! In fact, we had tailwinds or no winds for all but about 500 km of the whole trip around the block on that trip. Never repeated that again though...

I drove road trains Perth-East Coast & return weekly for 10 years & don't remember EVER having a tail wind!