Tomorrow’s fire danger is now predicted to be worse than originally forecast. The Illawarra-Shoalhaven region south of the city has been given a “catastrophic” fire danger rating, joining the Greater Sydney and Greater Hunter regions, which were assigned the ranking this morning.

It’s been announced that 300 schools in Sydney and across the state will be closed on Tuesday November 12, including Hornsby Heights Public School, Balgowlah North Public School, Ku-ring-gai High School, Lindfield Learning Village and Berowra Public School. Most school closures are around the north shore and northern suburbs, as well Blacktown in the west and Royal National Park in the south, but education minister Sarah Mitchell has said that number is likely to “rise considerably”. (See the full list of school closures here).

The Rural Fire Service (RFS) has authorised the immediate use of the standard emergency warning signal, an alarm played on radio and television before and during crises. Following the alarm, which will be played hourly until 7pm tonight, an announcement will be broadcast about the catastrophic bushfire danger.

A catastrophic forecast is the highest level of bushfire danger; this is the first time since the new ranking system was introduced in 2009 that the Greater Sydney area has been at catastrophic risk. The RFS says homes are not designed to withstand fires under these conditions and that “if a fire starts and takes hold during catastrophic fire danger conditions, lives and homes will be at risk”.

The Bureau of Meteorology has also issued a damaging wind warning for Monday afternoon in the Sydney metropolitan area. Tomorrow winds could reach up to 70kmh and temperatures are forecast to reach 37 degrees in the city. Ausgrid has cancelled all planned outages for maintenance across its network in the Greater Sydney and Greater Hunter regions.

The NSW Ambulance service has warned people to stay hydrated and pay attention to symptoms such as dizziness, headaches, racing pulse and nausea, as these can be signs of heat-related illness. It’s also warned people to remain aware of hazards such as embers, falling debris and reduced visibility.

This morning New South Wales premier Gladys Berejiklian declared a state of emergency, meaning the RFS has exceptional powers to do what is necessary to prevent and put out fires. The state of emergency will last for seven days and is the first in NSW since the 2013 Blue Mountains bushfires, which killed two people and destroyed more than 200 homes. Thirty-five local government areas – from Sydney’s beach suburbs all the way west to the Blue Mountains – could be affected by the fires.

More than 60 fires continue to burn across the state; more than half of those are uncontained.

Stay updated on the RFS Twitter feed and website for information on fires near you.