Dry conditions across the Murray Darling Basin will cut water allocations to South Australian irrigators.

Water Minister Ian Hunter says farmers will get an opening allocation of just 36 per cent for the 2016/17 water year.

Catchments across the basin are extremely dry and well-above average rainfall is needed to improve inflows to the river system.

“Earlier than usual allocation provides greater certainty, allowing irrigators and other water uses the confidence they need to prepare for the dry year ahead,” Mr Hunter said.

The latest allocation is based on a forecast for a very dry year, with only five in every 100 having lower inflows.

As well as their 36 per cent, irrigators in SA will be allowed to carry over up to 20 per cent of unused water allocation from 2015/16.

The allocation also comes as the Bureau of Meteorology released its latest climate outlook, which forecasts warmer than average temperatures across much of the country from May to July.

But the bureau has also tipped wetter than average conditions over the same period.