Widespread rain from 30-80mm is expected over the eastern half of NSW from storm activity, but the rain will also bring threats to waterways, drinking water and to people in bushfire-affected areas.
The good news is that the latest forecast from the Bureau of Meteorology has rain falling from Thursday over five days that includes: 30-50mm in the central, south and south-east areas of NSW, and between 30-80mm in the Northern, North-East and North-West areas. Depending on where the trough sits, the Riverina could also get rain of over 30mm.
Already some storms have been recorded in western NSW with falls over 30mm.
But there were a number of provisos though with the forecast: the rain will be localised, and totals may change depending on where storm cells form.
Also, the storms will bring a number of dangers in bushfire-affected zones where there could be landslips, landslides and trees weakened by fire could come down in storm wind gusts.
Gusts could be equal in intensity to southerly busters that have hit the coast in the last month. Some of the storms have the ability to bring heavy rain, the Bureau said.
WaterNSW said it was working to protect water quality in dam storages caused by ash run off.
Several precautionary measures have been taken including using silt curtains to stop ash being washed into Warragamba Dam by heavy rainfall.
Also the Murray-Darling Basin Authority has warned water quality is likely to be affected when it rains.
MDBA Executive Director of River Operations, Andrew Reynolds said people faced a double-edged sword.
"When we receive the much-needed rain to replenish depleted storages, we expect ash and sediment from the fires to be washed into some of our streams, rivers and dams," Mr Reynolds said.
"At this stage we know the fires will have an impact on water in the Upper Murray catchment above Hume Dam, but we will be able to make a full assessment when it's safe for agencies to enter these areas.
"This is the last thing our fire and drought ravaged communities need right now, but we will work closely with relevant agencies to manage the impacts and bring information to communities as they need it."
The MDBA said the ongoing dry, hot and windy conditions means water quality continued to deteriorate this past fortnight with nine new areas across New South Wales and Victoria now on red alert for blue-green algae. This brings the total number of red alerts to 20.
New South Wales sites with blue-green algae red alerts are: Menindee Lakes at Lake Wetherell; Mannus Lake; Lake Wyangala; Lake Windamere; Chifley Dam; Lake Wyangan at Griffith; Murrumbidgee River at Redbank Weir; Burrendong Dam; Macquarie River downstream of Burrendong Dam; Mehi River at Gundare; Namoi River downstream of Keepit Dam; Pindari Dam; Macintyre River at Boggabilla; Lake Copeton; Bogan River at Gongolgon; Barwon river downstream of Brewarrina weir; Darling River at Wilcannia
Victorian sites with blue-green algae red alerts are: Tullaroop Reservoir; Lake Eppalock; No 1 lagoon, Torrumbarry Irrigation Area.