Chifley Dam was at 100 per cent capacity in the most recent reading - as it has been for months - and Burrendong Dam, on the Macquarie downriver of Bathurst, was 71 per cent.

Water NSW says there is an 80 per cent chance that Wyangala Dam to Bathurst's south-west, which is on the Lachlan River, will fill by October and a 30 per cent chance that it will spill by the end of next month.

It was just under 88 per cent this week.

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To Bathurst's west, water flowed over Orange's Suma Park Dam wall last weekend - the first time it had happened since July 2016.

"I'd say what Orange would use in one day is going over there [the wall] in a couple of hours," Orange mayor Reg Kidd said.

Cr Kidd said the dam had reached the 80 per cent mark three-and-a-half weeks previously before getting to 90 per cent on July 11.

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The Bureau of Meteorology, meanwhile, has issued a flood watch for the Belubula River, which flows through the Blayney council area.

The exception in the region is Oberon Dam, which was at 54 per cent this week - though that is still much improved on early last year, when it was below 28 per cent and dropping by 0.5 per cent a week.

An indication of how much has changed and how quickly is that, around 18 months ago, Chifley Dam had fallen below 30 per cent and the Macquarie was no longer flowing at two gauging points downriver of the city.

Burrendong Dam was at 1.6 per cent at the time.

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Following a shift in the weather patterns, Chifley Dam hit capacity in September last year for the first time in four years and has been in rude good health ever since.

In terms of the spring outlook, the Bureau of Meteorology says rainfall for August to October is a greater than 80 per cent chance of exceeding the median for most of the eastern two-thirds of the mainland.