The change comes as NSW approaches a storm season threatening to be wetter than usual, Emergency Services Minister Steph Cooke says.
"The annual increased frequency of storms, strong winds and rain will coincide with a third consecutive La Nina, which means communities right across the state will remain on high alert," she told reporters on Thursday.
It's bad news for those in the flood-fatigued Northern Rivers and Hawkesbury-Nepean regions and inland parts of the state frequently and currently isolated by flooding.
"But it's important that we're not complacent," Ms Cooke said.
Bureau of Meteorology meteorologist Gabrielle Woodhouse says there's a heightened risk in summer as storms threaten to dump more rain on saturated catchments, which can lead to flash or riverine flooding.
Another storm is possible along central parts of the NSW coast on Thursday.
"But next week we're expecting a fairly significant system to move across NSW and at this stage, particularly from Tuesday or Wednesday, we're looking at widespread showers and thunderstorms," Ms Woodhouse said.
While storm season officially begins on Saturday, NSW has been hit with severe cells this week as flooding continues in parts of the state.
Major flood warnings remain along the Namoi, Bogan, Lachlan, Culgoa, Birrie, Bokhara and Narran Rivers.
Wee Waa and Warren in central west NSW have been cut off for several days.
The SES is dropping emergency supplies to communities that remain isolated, Ms Cooke says.
The agency will adopt the Australian Warning System - a nationally consistent model already used by the Rural Fire Service - on Friday.
A review of flooding around NSW earlier this year by chief scientist Mary O'Kane and former police commissioner Mick Fuller found the system needed an overhaul.
"Many people said that the weather and rainfall information received was inaccurate and that warnings and orders from the SES were inadequate," the report noted.
The warning system has three tiers.
When an advice alert is issued, it means something is happening and people should monitor conditions in case they worsen.
A watch and act warning means it is time to prepare to evacuate or be isolated.
The highest emergency warning means there is a present danger and people need to evacuate, find shelter or move to higher ground.
Warnings will continue to be sent via SMS, on the SES website and social media and via media outlets.
SES Commissioner Carlene York says the new system will solve confusion.
"It's important for all our community members to understand the messages that we send," she said.
The new system simplifies the messaging and makes clearer the expected response from the community.
Ms York says the agency has not had a day off this year.
"It's been an extraordinarily wet year and SES volunteers have been operational somewhere across the state every single day of 2022," she said.
People are advised to organise an emergency kit and prepare for storm season and potential flooding.
"Making safe decisions including evacuating when you are told and not driving through flooded roads and causeways will help protect yourself and your family this storm season," Ms York said.
The June budget earmarked more than $132 million for SES facilities, staff, resources and operational restructuring.
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