The NSW Blue Mountains suburb of Faulconbridge recorded the state's highest rainfall in the past 24 hours with 45mm.
The wet weather has been well received by firefighters, with fires burning near the Biriwal Bulga and Cottan-Bimbang national parks in the Mid North Coast region getting some help from the rain, with 38.2mm recorded in nearby Mount Seaview.
Areas around the South Coast and Southern Tablelands are predicted to receive up to 30mm but the BOM says the rain will be patchy.
People across Australia have taken to social media to celebrate the heavy rains hitting the east coast.
It was a welcome relief as it fell over firegrounds and allowed the Rural Fire Service to further strengthen containment lines.
"Although this rain won't extinguish all fires, it will certainly go a long way towards containment," the RFS said on Twitter.
However, the RFS reinforced the point that the summer's bushfire crisis wasn't yet over and they still had 1700 firefighters and support personnel battling blazes on Thursday.
The RFS said the favourable conditions allowed them to secure a number of "big wins" in their battle against some of the state's biggest fires, including the Northern Tablelands.
People were so happy, in fact, that on Thursday morning the word "rain" was trending nationally on Twitter.
NSW farmer Nick Andrews took the celebration one step further, shaving off the beard he had vowed to grow until an inch of rain fell on his sheep station, 30km southeast of Broken Hill.
He'd been growing the beard for 21 months by the time 36mm of rain fell on his property overnight.
"It was just torrential downpour. Flooded the place," he told ABC News on Thursday.
"There was probably two feet of water running past the house."
The Bureau of Meteorology (BoM) has forecast up to 100mm of rain to fall in some areas of the state between today and Sunday but added that other areas could receive very little.
But despite the celebration, the BoM warned rain could bring with it dangerous weather conditions, describing it as a "double-edged sword".
"An inland trough has been deepening across the state and is driving humid air across NSW, leading to thunderstorm activity across most districts," Mr Shabren told AAP on Thursday.
"We will continue to see severe thunderstorms throughout the week, with very heavy, short, sharp bursts of rainfall."
The NSW SES says this could increase the risk of flash flooding, falling trees and landslips where the fires have wiped out trees and growth.
"While the rain is welcomed, heavy rainfall and storms in fire-affected areas can lead to dangerous conditions such as a higher risk of flash flooding, falling trees and landslips," NSW SES Assistant Commissioner Paul Bailey said.
"In areas impacted by fires where vegetation has been destroyed, water from heavy rainfall can flow into riverbeds and we could see run-off in areas we wouldn't normally, resulting in flash flooding.
"The NSW SES is also asking residents in fire-affected areas to watch for possible landslips as the ground and roads can be damaged, therefore creating a higher risk of a potential slip."
The NSW SES has responded to more than190 flood and storm jobs across the state, mostly around Parkes, Port Stephens and Batemans Bay.
Severe thunderstorms that hit Victoria on Wednesday evening and are forecast to move over the east of the state bring with them additional fire risk, with the potential for lightning to ignite new fires.
Heavy rain and thunderstorms are also expected in NSW throughout the remainder of the week and the SES warned residents to prepare their properties by trimming overhanging branches, cleaning gutters and pipes, securing loose items in their backyards and not parking under trees or powerlines.
Bureau forecaster Jonathan How says while this week's rain is welcome the end of January and February are expected to be dry.
"Unfortunately the short-term to medium-term outlook is looking quite dry and warm," he said.