Thunderstorms and widespread rain are predicted for Canberra on Sunday and Monday, the Bureau of Meteorology said.
There is also a chance of storms moving through the ACT on Friday and Saturday.
The ACT Emergency Services Agency said recent storms meant the city was more likely to have trees come down and flooding during the coming rain.
Flash flooding hit Yass, Gundaroo and other towns around the territory at the end of October, shutting businesses and stranding cars.
There is a severe thunderstorm warning for parts of NSW and Victoria, as of 5pm Friday.
Canberrans should prepare for rain and flooding as soon as possible, emergency services said.
This includes checking gutters, trimming overhanging trees and branches, and keeping away from stormwater drains and catchments.
"If you are planning to travel, make sure you take extra caution on the roads and drive to the conditions," the ESA said.
"Do not drive, ride, walk or play in floodwaters. Remember, if it's flooded - forget it."
- For assistance in a storm or flood call the ACT State Emergency Service on 132 500, in a life-threatening emergency call Triple Zero (000).
