In Penrith, Sydney the Bureau of Meteorology (BOM) recorded a total of 61.4mm in just half an hour, much more than the area’s October average of 51mm.
According to the BOM, there is less than a 1% chance of that level of rain in Penrith.
Eland on the State’s mid-north coast received the most rainfall with 78.2mm.
Sydney, the Hunter region, and the rest of the mid-north coast received about 30-40mm.
The deluge sparked major flash-flooding, and multiple rescues took place.
— NSW SES West Sydney (@nswses_swr) October 17, 2018
— Weatherzone (@weatherzone) October 18, 2018
John-Luc Miller, from the NSW State Emergency Service (SES) said: “The flash flooding came through so quickly and the drain couldn’t handle the volume of water.”
In the 24-hour period beginning 9am Wednesday, Penrith received a total of 75mm.
Mr Simms said the SES were preparing for similar conditions as forecaster predict further deluges, Simms urged people to use common sense when driving.
Many will be welcoming the rains however, with the NSW Department of Primary Industries recently saying 98% of the State was still in drought.