After months of parched dry conditions, the Mountains was battered by record rainfall which took out the train line at Leura, cut power to thousands of homes and brought down trees.
The deluge saw a total of 415 millimetres of rain recorded at the Mt Boyce weather station from Thursday to Monday morning, including 158mm on Saturday and 137mm on Sunday.
The four-day blitz has already eclipsed February's average of 122mm and more rain fell in the four days than in the whole of the last nine months of 2019.
At Leura, the rain literally washed away the earth beneath the railway line.
The landslip halted trains which were replaced by buses west of Lawson. The head of Sydney Trains, Howard Collins, suggested it may be weeks rather than days to repair the track.
Several thousand homes lost power at various times on Saturday and Sunday.
Peter Payne, from Endeavour Energy, said houses right across the Mountains were affected, from Blaxland up to Mt Victoria. Most damage was caused by trees falling on to power lines.
A storm centre was established in Katoomba to coordinate repairs on the ground in the areas where there was the most storm damage.
While power was restored to some areas within 24 hours, other residents faced delays of several days. On Tuesday morning there were still almost 600 homes in the Mountains without power, in Katoomba (156), Warrimoo (114), Springwood (94), Blackheath (72), Mt Wilson (85) and Mt Tomah (71).
The SES took 372 calls over the four days, said local controller John Hughes. The SES had six teams operating, plus assistance from local RFS brigades. Residents reported smashed roofs, downed trees and localised flooding, Mr Hughes said.
At Dry Ridge Estate in the Megalong, a wedding party was stranded on Friday night when the only road out was covered by a metre of water.
Emergency personnel joked that being trapped in a winery was probably not a bad way to spend the night.
In Lurline St, Katoomba, a crane had to be brought in to cut down a huge tree and in Blackheath, another large tree was uprooted and crashed into a house in Romaine Street.
The damaged house was right next door to one which was completely destroyed by a tree in a wind storm last September.
At Mt Wilson several burnt trees, which had been earmarked for removal, fell down across roads.