A group of children have been rescued from a bus that became trapped in floodwaters that have hit Newcastle.

Emergency services were called to the University of Newcastle at Callaghan just before 5.30pm to find water halfway up the bus.

The State Emergency Service used an inflatable boat to rescue the nine children and driver.

Flash flooding across Newcastle has sparked a wave of requests for help, including eight flood rescues, according to the SES.

SES unit controller Ian Robinson said the rescues involved flooded houses and people trapped in flooded cars, including at the University of Newcastle, on Turton Road and on Maitland Road.

NSW SES are currently experiencing high call volumes due to weather and flash flooding impacts in #Newcastle and surrounding areas. Please be patient when you contact 132 500, we will get to your call as soon as possible. In life threatening emergencies call triple zero (000). pic.twitter.com/m9hU9auv0F

— NSW SES (@NSWSES) July 26, 2020

He said the organisation had six calls for flood support at 4pm, which increased to 73 by 5.30pm.

The Bureau of Meteorology has issued a severe weather warning for locations that could include Newcastle, Gosford, Sydney, Wollongong, Nowra and Batemans Bay.

Heavy #rain is continuing to lead to flash #flooding in a number of areas, including around #Newcastle and #Sydney. People are being urged to take extra care especially if driving in the current conditions. @NSWSES @nswpolice

— Bureau of Meteorology, New South Wales (@BOM_NSW) July 26, 2020

In the two hours to 4.35pm on Sunday, 70mm of rain fell at Williamtown and 74mm fell in the two hours to 5.13pm at Newcastle TAFE.

The low-pressure system is deepening off the NSW North Coast and is expected to move south in the coming days.

Newcastle MP Tim Crakanthorp posted on Twitter video from outside the Mayfield Hotel, where he said floodwaters had begun to make their way into the pub.

Flooding has made Newcastle roads very dangerous this evening. This video is from Maitland Road in Mayfield. If you must be driving tonight never, ever drive through floodwater. pic.twitter.com/OPRQMMnDnw

— Tim Crakanthorp (@crakanthorp) July 26, 2020

–ABC