The hot and dry weather is not suitable for the disease. With each dry week the risk of Downy Mildew affecting your crop decreases. Grape Berries are immune to Downy Mildew infection once they reach 2-6mm (Berries Peppercorn EL 30-31).
The risk in McLaren Vale on a Downy Mildew outbreak affecting grapegrowers yields is effectively zero.
The risk for the Adelaide Hills is higher, but still low as these vineyards are further away from developing immunity, however levels in the hills region are also low.